block/rbd.c | 202 ++++++++++++++++++++++++++++++++++++++++--- qapi/block-core.json | 5 +- 2 files changed, 192 insertions(+), 15 deletions(-)
This patch adds the support of preallocation (off/full) for the RBD
block driver.
If rbd_writesame() is available and supports zeroed buffers, we use
it to quickly fill the image when full preallocation is required.
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
v3:
- rebased on master
- filled with zeroed buffer [Max]
- used rbd_writesame() only when we can disable the discard of zeroed
buffers
- added 'since: 4.2' in qapi/block-core.json [Max]
- used buffer as large as the "stripe unit"
---
block/rbd.c | 202 ++++++++++++++++++++++++++++++++++++++++---
qapi/block-core.json | 5 +-
2 files changed, 192 insertions(+), 15 deletions(-)
diff --git a/block/rbd.c b/block/rbd.c
index 59757b3120..d923a5a26c 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -64,6 +64,7 @@
#define OBJ_MAX_SIZE (1UL << OBJ_DEFAULT_OBJ_ORDER)
#define RBD_MAX_SNAPS 100
+#define RBD_DEFAULT_CONCURRENT_OPS 10
/* The LIBRBD_SUPPORTS_IOVEC is defined in librbd.h */
#ifdef LIBRBD_SUPPORTS_IOVEC
@@ -104,6 +105,7 @@ typedef struct BDRVRBDState {
char *image_name;
char *snap;
uint64_t image_size;
+ bool ws_zero_supported; /* rbd_writesame() supports zeroed buffers */
} BDRVRBDState;
static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
@@ -333,6 +335,155 @@ static void qemu_rbd_memset(RADOSCB *rcb, int64_t offs)
}
}
+static int qemu_rbd_get_max_concurrent_ops(rados_t cluster)
+{
+ char buf[16];
+ int ret, max_concurrent_ops;
+
+ ret = rados_conf_get(cluster, "rbd_concurrent_management_ops", buf,
+ sizeof(buf));
+ if (ret < 0) {
+ return RBD_DEFAULT_CONCURRENT_OPS;
+ }
+
+ ret = qemu_strtoi(buf, NULL, 10, &max_concurrent_ops);
+ if (ret < 0) {
+ return RBD_DEFAULT_CONCURRENT_OPS;
+ }
+
+ return max_concurrent_ops;
+}
+
+static int qemu_rbd_do_truncate(rados_t cluster, rbd_image_t image,
+ int64_t offset, PreallocMode prealloc,
+ bool ws_zero_supported, Error **errp)
+{
+ uint64_t current_length;
+ char *buf = NULL;
+ int ret;
+
+ ret = rbd_get_size(image, ¤t_length);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "Failed to get file length");
+ goto out;
+ }
+
+ if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
+ error_setg(errp, "Cannot use preallocation for shrinking files");
+ ret = -ENOTSUP;
+ goto out;
+ }
+
+ switch (prealloc) {
+ case PREALLOC_MODE_FULL: {
+ uint64_t buf_size, current_offset = current_length;
+ ssize_t bytes;
+
+ ret = rbd_get_stripe_unit(image, &buf_size);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "Failed to get stripe unit");
+ goto out;
+ }
+
+ ret = rbd_resize(image, offset);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "Failed to resize file");
+ goto out;
+ }
+
+ buf = g_malloc0(buf_size);
+
+#ifdef LIBRBD_SUPPORTS_WRITESAME
+ if (ws_zero_supported) {
+ uint64_t writesame_max_size;
+ int max_concurrent_ops;
+
+ max_concurrent_ops = qemu_rbd_get_max_concurrent_ops(cluster);
+ /*
+ * We limit the rbd_writesame() size to avoid to spawn more then
+ * 'rbd_concurrent_management_ops' concurrent operations.
+ */
+ writesame_max_size = MIN(buf_size * max_concurrent_ops, INT_MAX);
+
+ while (offset - current_offset > buf_size) {
+ bytes = MIN(offset - current_offset, writesame_max_size);
+ /*
+ * rbd_writesame() supports only request where the size of the
+ * operation is multiple of buffer size.
+ */
+ bytes -= bytes % buf_size;
+
+ bytes = rbd_writesame(image, current_offset, bytes, buf,
+ buf_size, 0);
+ if (bytes < 0) {
+ ret = bytes;
+ error_setg_errno(errp, -ret,
+ "Failed to write for preallocation");
+ goto out;
+ }
+
+ current_offset += bytes;
+ }
+ }
+#endif /* LIBRBD_SUPPORTS_WRITESAME */
+
+ while (current_offset < offset) {
+ bytes = rbd_write(image, current_offset,
+ MIN(offset - current_offset, buf_size), buf);
+ if (bytes < 0) {
+ ret = bytes;
+ error_setg_errno(errp, -ret,
+ "Failed to write for preallocation");
+ goto out;
+ }
+
+ current_offset += bytes;
+ }
+
+ ret = rbd_flush(image);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "Failed to flush the file");
+ goto out;
+ }
+
+ break;
+ }
+ case PREALLOC_MODE_OFF:
+ ret = rbd_resize(image, offset);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "Failed to resize file");
+ goto out;
+ }
+ break;
+ default:
+ error_setg(errp, "Unsupported preallocation mode: %s",
+ PreallocMode_str(prealloc));
+ ret = -ENOTSUP;
+ goto out;
+ }
+
+ ret = 0;
+
+out:
+ g_free(buf);
+ return ret;
+}
+
+static bool qemu_rbd_writesame_zero_supported(rados_t *cluster)
+{
+ int ret = 1;
+
+#ifdef LIBRBD_SUPPORTS_WRITESAME
+ /*
+ * When "rbd_discard_on_zeroed_write_same" is not available, rbd_writesame()
+ * can discard requests with zeroed buffer.
+ */
+ ret = rados_conf_set(*cluster, "rbd_discard_on_zeroed_write_same", "false");
+#endif
+
+ return ret == 0;
+}
+
static QemuOptsList runtime_opts = {
.name = "rbd",
.head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
@@ -378,6 +529,7 @@ static int qemu_rbd_do_create(BlockdevCreateOptions *options,
BlockdevCreateOptionsRbd *opts = &options->u.rbd;
rados_t cluster;
rados_ioctx_t io_ctx;
+ rbd_image_t image;
int obj_order = 0;
int ret;
@@ -406,13 +558,23 @@ static int qemu_rbd_do_create(BlockdevCreateOptions *options,
return ret;
}
- ret = rbd_create(io_ctx, opts->location->image, opts->size, &obj_order);
+ ret = rbd_create(io_ctx, opts->location->image, 0, &obj_order);
if (ret < 0) {
error_setg_errno(errp, -ret, "error rbd create");
goto out;
}
- ret = 0;
+ ret = rbd_open(io_ctx, opts->location->image, &image, NULL);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "error rbd open");
+ goto out;
+ }
+
+ ret = qemu_rbd_do_truncate(cluster, image, opts->size, opts->preallocation,
+ qemu_rbd_writesame_zero_supported(&cluster),
+ errp);
+
+ rbd_close(image);
out:
rados_ioctx_destroy(io_ctx);
rados_shutdown(cluster);
@@ -433,6 +595,7 @@ static int coroutine_fn qemu_rbd_co_create_opts(const char *filename,
BlockdevOptionsRbd *loc;
Error *local_err = NULL;
const char *keypairs, *password_secret;
+ char *prealloc;
QDict *options = NULL;
int ret = 0;
@@ -451,6 +614,16 @@ static int coroutine_fn qemu_rbd_co_create_opts(const char *filename,
BLOCK_OPT_CLUSTER_SIZE, 0);
rbd_opts->has_cluster_size = (rbd_opts->cluster_size != 0);
+ prealloc = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC);
+ rbd_opts->preallocation = qapi_enum_parse(&PreallocMode_lookup, prealloc,
+ PREALLOC_MODE_OFF, &local_err);
+ g_free(prealloc);
+ if (local_err) {
+ ret = -EINVAL;
+ error_propagate(errp, local_err);
+ goto exit;
+ }
+
options = qdict_new();
qemu_rbd_parse_filename(filename, options, &local_err);
if (local_err) {
@@ -770,6 +943,7 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
s->snap = g_strdup(opts->snapshot);
s->image_name = g_strdup(opts->image);
+ s->ws_zero_supported = qemu_rbd_writesame_zero_supported(&s->cluster);
/* rbd_open is always r/w */
r = rbd_open(s->io_ctx, s->image_name, &s->image, s->snap);
@@ -1089,21 +1263,16 @@ static int coroutine_fn qemu_rbd_co_truncate(BlockDriverState *bs,
PreallocMode prealloc,
Error **errp)
{
- int r;
-
- if (prealloc != PREALLOC_MODE_OFF) {
- error_setg(errp, "Unsupported preallocation mode '%s'",
- PreallocMode_str(prealloc));
- return -ENOTSUP;
- }
+ BDRVRBDState *s = bs->opaque;
+ int ret;
- r = qemu_rbd_resize(bs, offset);
- if (r < 0) {
- error_setg_errno(errp, -r, "Failed to resize file");
- return r;
+ ret = qemu_rbd_do_truncate(s->cluster, s->image, offset, prealloc,
+ s->ws_zero_supported, errp);
+ if (ret == 0) {
+ s->image_size = offset;
}
- return 0;
+ return ret;
}
static int qemu_rbd_snap_create(BlockDriverState *bs,
@@ -1256,6 +1425,11 @@ static QemuOptsList qemu_rbd_create_opts = {
.type = QEMU_OPT_SIZE,
.help = "RBD object size"
},
+ {
+ .name = BLOCK_OPT_PREALLOC,
+ .type = QEMU_OPT_STRING,
+ .help = "Preallocation mode (allowed values: off, full)"
+ },
{
.name = "password-secret",
.type = QEMU_OPT_STRING,
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 0d43d4f37c..ff55171f8d 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -4346,13 +4346,16 @@
# point to a snapshot.
# @size Size of the virtual disk in bytes
# @cluster-size RBD object size
+# @preallocation Preallocation mode for the new image (since: 4.2)
+# (default: off; allowed values: off, full)
#
# Since: 2.12
##
{ 'struct': 'BlockdevCreateOptionsRbd',
'data': { 'location': 'BlockdevOptionsRbd',
'size': 'size',
- '*cluster-size' : 'size' } }
+ '*cluster-size' : 'size',
+ '*preallocation': 'PreallocMode' } }
##
# @BlockdevVmdkSubformat:
--
2.20.1
On Tue, 2019-07-23 at 09:13 +0200, Stefano Garzarella wrote:
> This patch adds the support of preallocation (off/full) for the RBD
> block driver.
> If rbd_writesame() is available and supports zeroed buffers, we use
> it to quickly fill the image when full preallocation is required.
>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
> v3:
> - rebased on master
> - filled with zeroed buffer [Max]
> - used rbd_writesame() only when we can disable the discard of zeroed
> buffers
> - added 'since: 4.2' in qapi/block-core.json [Max]
> - used buffer as large as the "stripe unit"
> ---
> block/rbd.c | 202 ++++++++++++++++++++++++++++++++++++++++---
> qapi/block-core.json | 5 +-
> 2 files changed, 192 insertions(+), 15 deletions(-)
>
> diff --git a/block/rbd.c b/block/rbd.c
> index 59757b3120..d923a5a26c 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -64,6 +64,7 @@
> #define OBJ_MAX_SIZE (1UL << OBJ_DEFAULT_OBJ_ORDER)
>
> #define RBD_MAX_SNAPS 100
> +#define RBD_DEFAULT_CONCURRENT_OPS 10
>
> /* The LIBRBD_SUPPORTS_IOVEC is defined in librbd.h */
> #ifdef LIBRBD_SUPPORTS_IOVEC
> @@ -104,6 +105,7 @@ typedef struct BDRVRBDState {
> char *image_name;
> char *snap;
> uint64_t image_size;
> + bool ws_zero_supported; /* rbd_writesame() supports zeroed buffers */
> } BDRVRBDState;
>
> static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
> @@ -333,6 +335,155 @@ static void qemu_rbd_memset(RADOSCB *rcb, int64_t offs)
> }
> }
>
> +static int qemu_rbd_get_max_concurrent_ops(rados_t cluster)
> +{
> + char buf[16];
> + int ret, max_concurrent_ops;
> +
> + ret = rados_conf_get(cluster, "rbd_concurrent_management_ops", buf,
> + sizeof(buf));
> + if (ret < 0) {
> + return RBD_DEFAULT_CONCURRENT_OPS;
> + }
> +
> + ret = qemu_strtoi(buf, NULL, 10, &max_concurrent_ops);
> + if (ret < 0) {
> + return RBD_DEFAULT_CONCURRENT_OPS;
> + }
> +
> + return max_concurrent_ops;
> +}
> +
> +static int qemu_rbd_do_truncate(rados_t cluster, rbd_image_t image,
> + int64_t offset, PreallocMode prealloc,
> + bool ws_zero_supported, Error **errp)
> +{
> + uint64_t current_length;
> + char *buf = NULL;
> + int ret;
> +
> + ret = rbd_get_size(image, ¤t_length);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Failed to get file length");
> + goto out;
> + }
> +
> + if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
> + error_setg(errp, "Cannot use preallocation for shrinking files");
> + ret = -ENOTSUP;
> + goto out;
> + }
> +
> + switch (prealloc) {
> + case PREALLOC_MODE_FULL: {
> + uint64_t buf_size, current_offset = current_length;
> + ssize_t bytes;
> +
> + ret = rbd_get_stripe_unit(image, &buf_size);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Failed to get stripe unit");
> + goto out;
> + }
> +
> + ret = rbd_resize(image, offset);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Failed to resize file");
> + goto out;
> + }
> +
> + buf = g_malloc0(buf_size);
> +
> +#ifdef LIBRBD_SUPPORTS_WRITESAME
> + if (ws_zero_supported) {
> + uint64_t writesame_max_size;
> + int max_concurrent_ops;
> +
> + max_concurrent_ops = qemu_rbd_get_max_concurrent_ops(cluster);
> + /*
> + * We limit the rbd_writesame() size to avoid to spawn more then
> + * 'rbd_concurrent_management_ops' concurrent operations.
> + */
> + writesame_max_size = MIN(buf_size * max_concurrent_ops, INT_MAX);
> +
> + while (offset - current_offset > buf_size) {
> + bytes = MIN(offset - current_offset, writesame_max_size);
> + /*
> + * rbd_writesame() supports only request where the size of the
> + * operation is multiple of buffer size.
> + */
> + bytes -= bytes % buf_size;
> +
> + bytes = rbd_writesame(image, current_offset, bytes, buf,
> + buf_size, 0);
> + if (bytes < 0) {
> + ret = bytes;
> + error_setg_errno(errp, -ret,
> + "Failed to write for preallocation");
> + goto out;
> + }
> +
> + current_offset += bytes;
> + }
> + }
> +#endif /* LIBRBD_SUPPORTS_WRITESAME */
> +
> + while (current_offset < offset) {
> + bytes = rbd_write(image, current_offset,
> + MIN(offset - current_offset, buf_size), buf);
> + if (bytes < 0) {
> + ret = bytes;
> + error_setg_errno(errp, -ret,
> + "Failed to write for preallocation");
> + goto out;
> + }
> +
> + current_offset += bytes;
> + }
> +
> + ret = rbd_flush(image);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Failed to flush the file");
> + goto out;
> + }
> +
> + break;
> + }
> + case PREALLOC_MODE_OFF:
> + ret = rbd_resize(image, offset);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Failed to resize file");
> + goto out;
> + }
> + break;
> + default:
> + error_setg(errp, "Unsupported preallocation mode: %s",
> + PreallocMode_str(prealloc));
> + ret = -ENOTSUP;
> + goto out;
> + }
> +
> + ret = 0;
> +
> +out:
> + g_free(buf);
> + return ret;
> +}
> +
> +static bool qemu_rbd_writesame_zero_supported(rados_t *cluster)
> +{
> + int ret = 1;
> +
> +#ifdef LIBRBD_SUPPORTS_WRITESAME
> + /*
> + * When "rbd_discard_on_zeroed_write_same" is not available, rbd_writesame()
> + * can discard requests with zeroed buffer.
> + */
> + ret = rados_conf_set(*cluster, "rbd_discard_on_zeroed_write_same", "false");
> +#endif
> +
> + return ret == 0;
> +}
> +
> static QemuOptsList runtime_opts = {
> .name = "rbd",
> .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
> @@ -378,6 +529,7 @@ static int qemu_rbd_do_create(BlockdevCreateOptions *options,
> BlockdevCreateOptionsRbd *opts = &options->u.rbd;
> rados_t cluster;
> rados_ioctx_t io_ctx;
> + rbd_image_t image;
> int obj_order = 0;
> int ret;
>
> @@ -406,13 +558,23 @@ static int qemu_rbd_do_create(BlockdevCreateOptions *options,
> return ret;
> }
>
> - ret = rbd_create(io_ctx, opts->location->image, opts->size, &obj_order);
> + ret = rbd_create(io_ctx, opts->location->image, 0, &obj_order);
> if (ret < 0) {
> error_setg_errno(errp, -ret, "error rbd create");
> goto out;
> }
>
> - ret = 0;
> + ret = rbd_open(io_ctx, opts->location->image, &image, NULL);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "error rbd open");
> + goto out;
> + }
> +
> + ret = qemu_rbd_do_truncate(cluster, image, opts->size, opts->preallocation,
> + qemu_rbd_writesame_zero_supported(&cluster),
> + errp);
> +
> + rbd_close(image);
> out:
> rados_ioctx_destroy(io_ctx);
> rados_shutdown(cluster);
> @@ -433,6 +595,7 @@ static int coroutine_fn qemu_rbd_co_create_opts(const char *filename,
> BlockdevOptionsRbd *loc;
> Error *local_err = NULL;
> const char *keypairs, *password_secret;
> + char *prealloc;
> QDict *options = NULL;
> int ret = 0;
>
> @@ -451,6 +614,16 @@ static int coroutine_fn qemu_rbd_co_create_opts(const char *filename,
> BLOCK_OPT_CLUSTER_SIZE, 0);
> rbd_opts->has_cluster_size = (rbd_opts->cluster_size != 0);
>
> + prealloc = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC);
> + rbd_opts->preallocation = qapi_enum_parse(&PreallocMode_lookup, prealloc,
> + PREALLOC_MODE_OFF, &local_err);
> + g_free(prealloc);
> + if (local_err) {
> + ret = -EINVAL;
> + error_propagate(errp, local_err);
> + goto exit;
> + }
> +
> options = qdict_new();
> qemu_rbd_parse_filename(filename, options, &local_err);
> if (local_err) {
> @@ -770,6 +943,7 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
>
> s->snap = g_strdup(opts->snapshot);
> s->image_name = g_strdup(opts->image);
> + s->ws_zero_supported = qemu_rbd_writesame_zero_supported(&s->cluster);
>
> /* rbd_open is always r/w */
> r = rbd_open(s->io_ctx, s->image_name, &s->image, s->snap);
> @@ -1089,21 +1263,16 @@ static int coroutine_fn qemu_rbd_co_truncate(BlockDriverState *bs,
> PreallocMode prealloc,
> Error **errp)
> {
> - int r;
> -
> - if (prealloc != PREALLOC_MODE_OFF) {
> - error_setg(errp, "Unsupported preallocation mode '%s'",
> - PreallocMode_str(prealloc));
> - return -ENOTSUP;
> - }
> + BDRVRBDState *s = bs->opaque;
> + int ret;
>
> - r = qemu_rbd_resize(bs, offset);
> - if (r < 0) {
> - error_setg_errno(errp, -r, "Failed to resize file");
> - return r;
> + ret = qemu_rbd_do_truncate(s->cluster, s->image, offset, prealloc,
> + s->ws_zero_supported, errp);
> + if (ret == 0) {
> + s->image_size = offset;
> }
>
> - return 0;
> + return ret;
> }
>
> static int qemu_rbd_snap_create(BlockDriverState *bs,
> @@ -1256,6 +1425,11 @@ static QemuOptsList qemu_rbd_create_opts = {
> .type = QEMU_OPT_SIZE,
> .help = "RBD object size"
> },
> + {
> + .name = BLOCK_OPT_PREALLOC,
> + .type = QEMU_OPT_STRING,
> + .help = "Preallocation mode (allowed values: off, full)"
> + },
> {
> .name = "password-secret",
> .type = QEMU_OPT_STRING,
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 0d43d4f37c..ff55171f8d 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -4346,13 +4346,16 @@
> # point to a snapshot.
> # @size Size of the virtual disk in bytes
> # @cluster-size RBD object size
> +# @preallocation Preallocation mode for the new image (since: 4.2)
> +# (default: off; allowed values: off, full)
> #
> # Since: 2.12
> ##
> { 'struct': 'BlockdevCreateOptionsRbd',
> 'data': { 'location': 'BlockdevOptionsRbd',
> 'size': 'size',
> - '*cluster-size' : 'size' } }
> + '*cluster-size' : 'size',
> + '*preallocation': 'PreallocMode' } }
>
> ##
> # @BlockdevVmdkSubformat:
I think I don't see anything obviously wrong, but note that I don't know ceph yet,
thus I might have missed something.
So:
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Best regards,
Maxim Levitsky
On Tue, Jul 23, 2019 at 3:13 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> This patch adds the support of preallocation (off/full) for the RBD
> block driver.
> If rbd_writesame() is available and supports zeroed buffers, we use
> it to quickly fill the image when full preallocation is required.
>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
> v3:
> - rebased on master
> - filled with zeroed buffer [Max]
> - used rbd_writesame() only when we can disable the discard of zeroed
> buffers
> - added 'since: 4.2' in qapi/block-core.json [Max]
> - used buffer as large as the "stripe unit"
> ---
> block/rbd.c | 202 ++++++++++++++++++++++++++++++++++++++++---
> qapi/block-core.json | 5 +-
> 2 files changed, 192 insertions(+), 15 deletions(-)
>
> diff --git a/block/rbd.c b/block/rbd.c
> index 59757b3120..d923a5a26c 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -64,6 +64,7 @@
> #define OBJ_MAX_SIZE (1UL << OBJ_DEFAULT_OBJ_ORDER)
>
> #define RBD_MAX_SNAPS 100
> +#define RBD_DEFAULT_CONCURRENT_OPS 10
>
> /* The LIBRBD_SUPPORTS_IOVEC is defined in librbd.h */
> #ifdef LIBRBD_SUPPORTS_IOVEC
> @@ -104,6 +105,7 @@ typedef struct BDRVRBDState {
> char *image_name;
> char *snap;
> uint64_t image_size;
> + bool ws_zero_supported; /* rbd_writesame() supports zeroed buffers */
> } BDRVRBDState;
>
> static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
> @@ -333,6 +335,155 @@ static void qemu_rbd_memset(RADOSCB *rcb, int64_t offs)
> }
> }
>
> +static int qemu_rbd_get_max_concurrent_ops(rados_t cluster)
> +{
> + char buf[16];
> + int ret, max_concurrent_ops;
> +
> + ret = rados_conf_get(cluster, "rbd_concurrent_management_ops", buf,
> + sizeof(buf));
> + if (ret < 0) {
> + return RBD_DEFAULT_CONCURRENT_OPS;
> + }
> +
> + ret = qemu_strtoi(buf, NULL, 10, &max_concurrent_ops);
> + if (ret < 0) {
> + return RBD_DEFAULT_CONCURRENT_OPS;
> + }
> +
> + return max_concurrent_ops;
> +}
> +
> +static int qemu_rbd_do_truncate(rados_t cluster, rbd_image_t image,
> + int64_t offset, PreallocMode prealloc,
> + bool ws_zero_supported, Error **errp)
> +{
> + uint64_t current_length;
> + char *buf = NULL;
> + int ret;
> +
> + ret = rbd_get_size(image, ¤t_length);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Failed to get file length");
> + goto out;
> + }
> +
> + if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
> + error_setg(errp, "Cannot use preallocation for shrinking files");
> + ret = -ENOTSUP;
> + goto out;
> + }
> +
> + switch (prealloc) {
> + case PREALLOC_MODE_FULL: {
> + uint64_t buf_size, current_offset = current_length;
> + ssize_t bytes;
> +
> + ret = rbd_get_stripe_unit(image, &buf_size);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Failed to get stripe unit");
> + goto out;
> + }
> +
> + ret = rbd_resize(image, offset);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Failed to resize file");
> + goto out;
> + }
> +
> + buf = g_malloc0(buf_size);
> +
> +#ifdef LIBRBD_SUPPORTS_WRITESAME
> + if (ws_zero_supported) {
> + uint64_t writesame_max_size;
> + int max_concurrent_ops;
> +
> + max_concurrent_ops = qemu_rbd_get_max_concurrent_ops(cluster);
> + /*
> + * We limit the rbd_writesame() size to avoid to spawn more then
> + * 'rbd_concurrent_management_ops' concurrent operations.
> + */
> + writesame_max_size = MIN(buf_size * max_concurrent_ops, INT_MAX);
In the most efficient world, the 'buf_size' would be some small, fixed
power of 2 value (like 512 bytes) since there isn't much need to send
extra zeroes. You would then want to writesame the full stripe period
(if possible), where a stripe period is the data block object size
(defaults to 4MiB and is availble via 'rbd_stat') * the stripe count.
In this case, the stripe count becomes the number of in-flight IOs.
Therefore, you could substitute its value w/ the max_concurrent_ops to
ensure you are issuing exactly max_concurrent_ops IOs per
rbd_writesame call.
> +
> + while (offset - current_offset > buf_size) {
> + bytes = MIN(offset - current_offset, writesame_max_size);
> + /*
> + * rbd_writesame() supports only request where the size of the
> + * operation is multiple of buffer size.
> + */
> + bytes -= bytes % buf_size;
> +
> + bytes = rbd_writesame(image, current_offset, bytes, buf,
> + buf_size, 0);
If the RBD in-memory cache is enabled during this operation, the
writesame will effectively just be turned into a write. Therefore,
when pre-allocating, you will want to disable the cache.
> + if (bytes < 0) {
> + ret = bytes;
> + error_setg_errno(errp, -ret,
> + "Failed to write for preallocation");
> + goto out;
> + }
> +
> + current_offset += bytes;
> + }
> + }
> +#endif /* LIBRBD_SUPPORTS_WRITESAME */
> +
> + while (current_offset < offset) {
> + bytes = rbd_write(image, current_offset,
> + MIN(offset - current_offset, buf_size), buf);
> + if (bytes < 0) {
> + ret = bytes;
> + error_setg_errno(errp, -ret,
> + "Failed to write for preallocation");
> + goto out;
> + }
> +
> + current_offset += bytes;
> + }
> +
> + ret = rbd_flush(image);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Failed to flush the file");
> + goto out;
> + }
> +
> + break;
> + }
> + case PREALLOC_MODE_OFF:
> + ret = rbd_resize(image, offset);
I'm not familiar enough w/ the QEMU block code, but why would the
PREALLOC_MODE_FULL case not need to resize the image?
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Failed to resize file");
> + goto out;
> + }
> + break;
> + default:
> + error_setg(errp, "Unsupported preallocation mode: %s",
> + PreallocMode_str(prealloc));
> + ret = -ENOTSUP;
> + goto out;
> + }
> +
> + ret = 0;
> +
> +out:
> + g_free(buf);
> + return ret;
> +}
> +
> +static bool qemu_rbd_writesame_zero_supported(rados_t *cluster)
> +{
> + int ret = 1;
> +
> +#ifdef LIBRBD_SUPPORTS_WRITESAME
> + /*
> + * When "rbd_discard_on_zeroed_write_same" is not available, rbd_writesame()
> + * can discard requests with zeroed buffer.
> + */
> + ret = rados_conf_set(*cluster, "rbd_discard_on_zeroed_write_same", "false");
> +#endif
> +
> + return ret == 0;
> +}
> +
> static QemuOptsList runtime_opts = {
> .name = "rbd",
> .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
> @@ -378,6 +529,7 @@ static int qemu_rbd_do_create(BlockdevCreateOptions *options,
> BlockdevCreateOptionsRbd *opts = &options->u.rbd;
> rados_t cluster;
> rados_ioctx_t io_ctx;
> + rbd_image_t image;
> int obj_order = 0;
> int ret;
>
> @@ -406,13 +558,23 @@ static int qemu_rbd_do_create(BlockdevCreateOptions *options,
> return ret;
> }
>
> - ret = rbd_create(io_ctx, opts->location->image, opts->size, &obj_order);
> + ret = rbd_create(io_ctx, opts->location->image, 0, &obj_order);
> if (ret < 0) {
> error_setg_errno(errp, -ret, "error rbd create");
> goto out;
> }
>
> - ret = 0;
> + ret = rbd_open(io_ctx, opts->location->image, &image, NULL);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "error rbd open");
> + goto out;
> + }
> +
> + ret = qemu_rbd_do_truncate(cluster, image, opts->size, opts->preallocation,
> + qemu_rbd_writesame_zero_supported(&cluster),
> + errp);
> +
> + rbd_close(image);
> out:
> rados_ioctx_destroy(io_ctx);
> rados_shutdown(cluster);
> @@ -433,6 +595,7 @@ static int coroutine_fn qemu_rbd_co_create_opts(const char *filename,
> BlockdevOptionsRbd *loc;
> Error *local_err = NULL;
> const char *keypairs, *password_secret;
> + char *prealloc;
> QDict *options = NULL;
> int ret = 0;
>
> @@ -451,6 +614,16 @@ static int coroutine_fn qemu_rbd_co_create_opts(const char *filename,
> BLOCK_OPT_CLUSTER_SIZE, 0);
> rbd_opts->has_cluster_size = (rbd_opts->cluster_size != 0);
>
> + prealloc = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC);
> + rbd_opts->preallocation = qapi_enum_parse(&PreallocMode_lookup, prealloc,
> + PREALLOC_MODE_OFF, &local_err);
> + g_free(prealloc);
> + if (local_err) {
> + ret = -EINVAL;
> + error_propagate(errp, local_err);
> + goto exit;
> + }
> +
> options = qdict_new();
> qemu_rbd_parse_filename(filename, options, &local_err);
> if (local_err) {
> @@ -770,6 +943,7 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
>
> s->snap = g_strdup(opts->snapshot);
> s->image_name = g_strdup(opts->image);
> + s->ws_zero_supported = qemu_rbd_writesame_zero_supported(&s->cluster);
>
> /* rbd_open is always r/w */
> r = rbd_open(s->io_ctx, s->image_name, &s->image, s->snap);
> @@ -1089,21 +1263,16 @@ static int coroutine_fn qemu_rbd_co_truncate(BlockDriverState *bs,
> PreallocMode prealloc,
> Error **errp)
> {
> - int r;
> -
> - if (prealloc != PREALLOC_MODE_OFF) {
> - error_setg(errp, "Unsupported preallocation mode '%s'",
> - PreallocMode_str(prealloc));
> - return -ENOTSUP;
> - }
> + BDRVRBDState *s = bs->opaque;
> + int ret;
>
> - r = qemu_rbd_resize(bs, offset);
> - if (r < 0) {
> - error_setg_errno(errp, -r, "Failed to resize file");
> - return r;
> + ret = qemu_rbd_do_truncate(s->cluster, s->image, offset, prealloc,
> + s->ws_zero_supported, errp);
> + if (ret == 0) {
> + s->image_size = offset;
> }
>
> - return 0;
> + return ret;
> }
>
> static int qemu_rbd_snap_create(BlockDriverState *bs,
> @@ -1256,6 +1425,11 @@ static QemuOptsList qemu_rbd_create_opts = {
> .type = QEMU_OPT_SIZE,
> .help = "RBD object size"
> },
> + {
> + .name = BLOCK_OPT_PREALLOC,
> + .type = QEMU_OPT_STRING,
> + .help = "Preallocation mode (allowed values: off, full)"
> + },
> {
> .name = "password-secret",
> .type = QEMU_OPT_STRING,
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 0d43d4f37c..ff55171f8d 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -4346,13 +4346,16 @@
> # point to a snapshot.
> # @size Size of the virtual disk in bytes
> # @cluster-size RBD object size
> +# @preallocation Preallocation mode for the new image (since: 4.2)
> +# (default: off; allowed values: off, full)
> #
> # Since: 2.12
> ##
> { 'struct': 'BlockdevCreateOptionsRbd',
> 'data': { 'location': 'BlockdevOptionsRbd',
> 'size': 'size',
> - '*cluster-size' : 'size' } }
> + '*cluster-size' : 'size',
> + '*preallocation': 'PreallocMode' } }
>
> ##
> # @BlockdevVmdkSubformat:
> --
> 2.20.1
>
--
Jason
On Wed, Jul 24, 2019 at 01:48:42PM -0400, Jason Dillaman wrote:
> On Tue, Jul 23, 2019 at 3:13 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
> >
> > This patch adds the support of preallocation (off/full) for the RBD
> > block driver.
> > If rbd_writesame() is available and supports zeroed buffers, we use
> > it to quickly fill the image when full preallocation is required.
> >
> > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> > ---
> > v3:
> > - rebased on master
> > - filled with zeroed buffer [Max]
> > - used rbd_writesame() only when we can disable the discard of zeroed
> > buffers
> > - added 'since: 4.2' in qapi/block-core.json [Max]
> > - used buffer as large as the "stripe unit"
> > ---
> > block/rbd.c | 202 ++++++++++++++++++++++++++++++++++++++++---
> > qapi/block-core.json | 5 +-
> > 2 files changed, 192 insertions(+), 15 deletions(-)
> >
> > diff --git a/block/rbd.c b/block/rbd.c
> > index 59757b3120..d923a5a26c 100644
> > --- a/block/rbd.c
> > +++ b/block/rbd.c
> > @@ -64,6 +64,7 @@
> > #define OBJ_MAX_SIZE (1UL << OBJ_DEFAULT_OBJ_ORDER)
> >
> > #define RBD_MAX_SNAPS 100
> > +#define RBD_DEFAULT_CONCURRENT_OPS 10
> >
> > /* The LIBRBD_SUPPORTS_IOVEC is defined in librbd.h */
> > #ifdef LIBRBD_SUPPORTS_IOVEC
> > @@ -104,6 +105,7 @@ typedef struct BDRVRBDState {
> > char *image_name;
> > char *snap;
> > uint64_t image_size;
> > + bool ws_zero_supported; /* rbd_writesame() supports zeroed buffers */
> > } BDRVRBDState;
> >
> > static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
> > @@ -333,6 +335,155 @@ static void qemu_rbd_memset(RADOSCB *rcb, int64_t offs)
> > }
> > }
> >
> > +static int qemu_rbd_get_max_concurrent_ops(rados_t cluster)
> > +{
> > + char buf[16];
> > + int ret, max_concurrent_ops;
> > +
> > + ret = rados_conf_get(cluster, "rbd_concurrent_management_ops", buf,
> > + sizeof(buf));
> > + if (ret < 0) {
> > + return RBD_DEFAULT_CONCURRENT_OPS;
> > + }
> > +
> > + ret = qemu_strtoi(buf, NULL, 10, &max_concurrent_ops);
> > + if (ret < 0) {
> > + return RBD_DEFAULT_CONCURRENT_OPS;
> > + }
> > +
> > + return max_concurrent_ops;
> > +}
> > +
> > +static int qemu_rbd_do_truncate(rados_t cluster, rbd_image_t image,
> > + int64_t offset, PreallocMode prealloc,
> > + bool ws_zero_supported, Error **errp)
> > +{
> > + uint64_t current_length;
> > + char *buf = NULL;
> > + int ret;
> > +
> > + ret = rbd_get_size(image, ¤t_length);
> > + if (ret < 0) {
> > + error_setg_errno(errp, -ret, "Failed to get file length");
> > + goto out;
> > + }
> > +
> > + if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
> > + error_setg(errp, "Cannot use preallocation for shrinking files");
> > + ret = -ENOTSUP;
> > + goto out;
> > + }
> > +
> > + switch (prealloc) {
> > + case PREALLOC_MODE_FULL: {
> > + uint64_t buf_size, current_offset = current_length;
> > + ssize_t bytes;
> > +
> > + ret = rbd_get_stripe_unit(image, &buf_size);
> > + if (ret < 0) {
> > + error_setg_errno(errp, -ret, "Failed to get stripe unit");
> > + goto out;
> > + }
> > +
> > + ret = rbd_resize(image, offset);
> > + if (ret < 0) {
> > + error_setg_errno(errp, -ret, "Failed to resize file");
> > + goto out;
> > + }
> > +
> > + buf = g_malloc0(buf_size);
> > +
> > +#ifdef LIBRBD_SUPPORTS_WRITESAME
> > + if (ws_zero_supported) {
> > + uint64_t writesame_max_size;
> > + int max_concurrent_ops;
> > +
> > + max_concurrent_ops = qemu_rbd_get_max_concurrent_ops(cluster);
> > + /*
> > + * We limit the rbd_writesame() size to avoid to spawn more then
> > + * 'rbd_concurrent_management_ops' concurrent operations.
> > + */
> > + writesame_max_size = MIN(buf_size * max_concurrent_ops, INT_MAX);
>
> In the most efficient world, the 'buf_size' would be some small, fixed
> power of 2 value (like 512 bytes) since there isn't much need to send
> extra zeroes. You would then want to writesame the full stripe period
> (if possible), where a stripe period is the data block object size
> (defaults to 4MiB and is availble via 'rbd_stat') * the stripe count.
> In this case, the stripe count becomes the number of in-flight IOs.
> Therefore, you could substitute its value w/ the max_concurrent_ops to
> ensure you are issuing exactly max_concurrent_ops IOs per
> rbd_writesame call.
>
Initially, I had a fixed buffer size to 4 KiB, but I noted that, when
we didn't use writesame, the rbd_write() was very slow, so I used the
stripe unit as a buffer size.
Do you think is better to have a small buffer (512 byte) when we use
writesame or a 'stripe unit' buffer when we can't use it?
> > +
> > + while (offset - current_offset > buf_size) {
> > + bytes = MIN(offset - current_offset, writesame_max_size);
> > + /*
> > + * rbd_writesame() supports only request where the size of the
> > + * operation is multiple of buffer size.
> > + */
> > + bytes -= bytes % buf_size;
> > +
> > + bytes = rbd_writesame(image, current_offset, bytes, buf,
> > + buf_size, 0);
>
> If the RBD in-memory cache is enabled during this operation, the
> writesame will effectively just be turned into a write. Therefore,
> when pre-allocating, you will want to disable the cache.
>
During the creation, when preallocation is often used, we disable the cache:
static int qemu_rbd_do_create(BlockdevCreateOptions *options,
const char *keypairs, const char *password_secret,
Error **errp)
{
...
ret = qemu_rbd_connect(&cluster, &io_ctx, opts->location, false, keypairs,
^^ cache param
...
}
Do you think I should disable it in any case during the preallocation?
> > + if (bytes < 0) {
> > + ret = bytes;
> > + error_setg_errno(errp, -ret,
> > + "Failed to write for preallocation");
> > + goto out;
> > + }
> > +
> > + current_offset += bytes;
> > + }
> > + }
> > +#endif /* LIBRBD_SUPPORTS_WRITESAME */
> > +
> > + while (current_offset < offset) {
> > + bytes = rbd_write(image, current_offset,
> > + MIN(offset - current_offset, buf_size), buf);
> > + if (bytes < 0) {
> > + ret = bytes;
> > + error_setg_errno(errp, -ret,
> > + "Failed to write for preallocation");
> > + goto out;
> > + }
> > +
> > + current_offset += bytes;
> > + }
> > +
> > + ret = rbd_flush(image);
> > + if (ret < 0) {
> > + error_setg_errno(errp, -ret, "Failed to flush the file");
> > + goto out;
> > + }
> > +
> > + break;
> > + }
> > + case PREALLOC_MODE_OFF:
> > + ret = rbd_resize(image, offset);
>
> I'm not familiar enough w/ the QEMU block code, but why would the
> PREALLOC_MODE_FULL case not need to resize the image?
PREALLOC_MODE_FULL need too, I did it just before the g_malloc0() in
this patch :-)
Thanks,
Stefano
On Thu, Jul 25, 2019 at 4:13 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> On Wed, Jul 24, 2019 at 01:48:42PM -0400, Jason Dillaman wrote:
> > On Tue, Jul 23, 2019 at 3:13 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
> > >
> > > This patch adds the support of preallocation (off/full) for the RBD
> > > block driver.
> > > If rbd_writesame() is available and supports zeroed buffers, we use
> > > it to quickly fill the image when full preallocation is required.
> > >
> > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> > > ---
> > > v3:
> > > - rebased on master
> > > - filled with zeroed buffer [Max]
> > > - used rbd_writesame() only when we can disable the discard of zeroed
> > > buffers
> > > - added 'since: 4.2' in qapi/block-core.json [Max]
> > > - used buffer as large as the "stripe unit"
> > > ---
> > > block/rbd.c | 202 ++++++++++++++++++++++++++++++++++++++++---
> > > qapi/block-core.json | 5 +-
> > > 2 files changed, 192 insertions(+), 15 deletions(-)
> > >
> > > diff --git a/block/rbd.c b/block/rbd.c
> > > index 59757b3120..d923a5a26c 100644
> > > --- a/block/rbd.c
> > > +++ b/block/rbd.c
> > > @@ -64,6 +64,7 @@
> > > #define OBJ_MAX_SIZE (1UL << OBJ_DEFAULT_OBJ_ORDER)
> > >
> > > #define RBD_MAX_SNAPS 100
> > > +#define RBD_DEFAULT_CONCURRENT_OPS 10
> > >
> > > /* The LIBRBD_SUPPORTS_IOVEC is defined in librbd.h */
> > > #ifdef LIBRBD_SUPPORTS_IOVEC
> > > @@ -104,6 +105,7 @@ typedef struct BDRVRBDState {
> > > char *image_name;
> > > char *snap;
> > > uint64_t image_size;
> > > + bool ws_zero_supported; /* rbd_writesame() supports zeroed buffers */
> > > } BDRVRBDState;
> > >
> > > static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
> > > @@ -333,6 +335,155 @@ static void qemu_rbd_memset(RADOSCB *rcb, int64_t offs)
> > > }
> > > }
> > >
> > > +static int qemu_rbd_get_max_concurrent_ops(rados_t cluster)
> > > +{
> > > + char buf[16];
> > > + int ret, max_concurrent_ops;
> > > +
> > > + ret = rados_conf_get(cluster, "rbd_concurrent_management_ops", buf,
> > > + sizeof(buf));
> > > + if (ret < 0) {
> > > + return RBD_DEFAULT_CONCURRENT_OPS;
> > > + }
> > > +
> > > + ret = qemu_strtoi(buf, NULL, 10, &max_concurrent_ops);
> > > + if (ret < 0) {
> > > + return RBD_DEFAULT_CONCURRENT_OPS;
> > > + }
> > > +
> > > + return max_concurrent_ops;
> > > +}
> > > +
> > > +static int qemu_rbd_do_truncate(rados_t cluster, rbd_image_t image,
> > > + int64_t offset, PreallocMode prealloc,
> > > + bool ws_zero_supported, Error **errp)
> > > +{
> > > + uint64_t current_length;
> > > + char *buf = NULL;
> > > + int ret;
> > > +
> > > + ret = rbd_get_size(image, ¤t_length);
> > > + if (ret < 0) {
> > > + error_setg_errno(errp, -ret, "Failed to get file length");
> > > + goto out;
> > > + }
> > > +
> > > + if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
> > > + error_setg(errp, "Cannot use preallocation for shrinking files");
> > > + ret = -ENOTSUP;
> > > + goto out;
> > > + }
> > > +
> > > + switch (prealloc) {
> > > + case PREALLOC_MODE_FULL: {
> > > + uint64_t buf_size, current_offset = current_length;
> > > + ssize_t bytes;
> > > +
> > > + ret = rbd_get_stripe_unit(image, &buf_size);
> > > + if (ret < 0) {
> > > + error_setg_errno(errp, -ret, "Failed to get stripe unit");
> > > + goto out;
> > > + }
> > > +
> > > + ret = rbd_resize(image, offset);
> > > + if (ret < 0) {
> > > + error_setg_errno(errp, -ret, "Failed to resize file");
> > > + goto out;
> > > + }
> > > +
> > > + buf = g_malloc0(buf_size);
> > > +
> > > +#ifdef LIBRBD_SUPPORTS_WRITESAME
> > > + if (ws_zero_supported) {
> > > + uint64_t writesame_max_size;
> > > + int max_concurrent_ops;
> > > +
> > > + max_concurrent_ops = qemu_rbd_get_max_concurrent_ops(cluster);
> > > + /*
> > > + * We limit the rbd_writesame() size to avoid to spawn more then
> > > + * 'rbd_concurrent_management_ops' concurrent operations.
> > > + */
> > > + writesame_max_size = MIN(buf_size * max_concurrent_ops, INT_MAX);
> >
> > In the most efficient world, the 'buf_size' would be some small, fixed
> > power of 2 value (like 512 bytes) since there isn't much need to send
> > extra zeroes. You would then want to writesame the full stripe period
> > (if possible), where a stripe period is the data block object size
> > (defaults to 4MiB and is availble via 'rbd_stat') * the stripe count.
> > In this case, the stripe count becomes the number of in-flight IOs.
> > Therefore, you could substitute its value w/ the max_concurrent_ops to
> > ensure you are issuing exactly max_concurrent_ops IOs per
> > rbd_writesame call.
> >
>
> Initially, I had a fixed buffer size to 4 KiB, but I noted that, when
> we didn't use writesame, the rbd_write() was very slow, so I used the
> stripe unit as a buffer size.
>
> Do you think is better to have a small buffer (512 byte) when we use
> writesame or a 'stripe unit' buffer when we can't use it?
I'd use a small buffer for rbd_writesame and then just reallocate the
buffer to a larger size for "rbd_write". It would be most efficient to
allocate a "object size * max concurrent ops" -sized buffer (up to
some reasonable maximum) for the standard rbd_write. Just make sure
your "rbd_writes" offsets / length is aligned to the stripe period for
the most efficient IO (i.e. the initial write might be smaller than
the stripe period if the starting offset is unaligned).
> > > +
> > > + while (offset - current_offset > buf_size) {
> > > + bytes = MIN(offset - current_offset, writesame_max_size);
> > > + /*
> > > + * rbd_writesame() supports only request where the size of the
> > > + * operation is multiple of buffer size.
> > > + */
> > > + bytes -= bytes % buf_size;
> > > +
> > > + bytes = rbd_writesame(image, current_offset, bytes, buf,
> > > + buf_size, 0);
> >
> > If the RBD in-memory cache is enabled during this operation, the
> > writesame will effectively just be turned into a write. Therefore,
> > when pre-allocating, you will want to disable the cache.
> >
>
> During the creation, when preallocation is often used, we disable the cache:
>
> static int qemu_rbd_do_create(BlockdevCreateOptions *options,
> const char *keypairs, const char *password_secret,
> Error **errp)
> {
> ...
>
> ret = qemu_rbd_connect(&cluster, &io_ctx, opts->location, false, keypairs,
> ^^ cache param
> ...
> }
>
>
> Do you think I should disable it in any case during the preallocation?
Assuming you can grow an image w/ full preallocation, I would
definitely want to ensure that the cache is disabled since otherwise
you would just be performing regular (non-offloaded) writes.
>
>
> > > + if (bytes < 0) {
> > > + ret = bytes;
> > > + error_setg_errno(errp, -ret,
> > > + "Failed to write for preallocation");
> > > + goto out;
> > > + }
> > > +
> > > + current_offset += bytes;
> > > + }
> > > + }
> > > +#endif /* LIBRBD_SUPPORTS_WRITESAME */
> > > +
> > > + while (current_offset < offset) {
> > > + bytes = rbd_write(image, current_offset,
> > > + MIN(offset - current_offset, buf_size), buf);
> > > + if (bytes < 0) {
> > > + ret = bytes;
> > > + error_setg_errno(errp, -ret,
> > > + "Failed to write for preallocation");
> > > + goto out;
> > > + }
> > > +
> > > + current_offset += bytes;
> > > + }
> > > +
> > > + ret = rbd_flush(image);
> > > + if (ret < 0) {
> > > + error_setg_errno(errp, -ret, "Failed to flush the file");
> > > + goto out;
> > > + }
> > > +
> > > + break;
> > > + }
> > > + case PREALLOC_MODE_OFF:
> > > + ret = rbd_resize(image, offset);
> >
> > I'm not familiar enough w/ the QEMU block code, but why would the
> > PREALLOC_MODE_FULL case not need to resize the image?
>
> PREALLOC_MODE_FULL need too, I did it just before the g_malloc0() in
> this patch :-)
Sorry I missed it. Would it make more sense to just do it before the
switch statement so that you don't duplicate the code and resulting
error handling? I guess just validate that the prealloc mode is
supported before issuing the resize.
> Thanks,
> Stefano
--
Jason
On Thu, Jul 25, 2019 at 09:30:30AM -0400, Jason Dillaman wrote:
> On Thu, Jul 25, 2019 at 4:13 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
> >
> > On Wed, Jul 24, 2019 at 01:48:42PM -0400, Jason Dillaman wrote:
> > > On Tue, Jul 23, 2019 at 3:13 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
> > > >
> > > > This patch adds the support of preallocation (off/full) for the RBD
> > > > block driver.
> > > > If rbd_writesame() is available and supports zeroed buffers, we use
> > > > it to quickly fill the image when full preallocation is required.
> > > >
> > > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> > > > ---
> > > > v3:
> > > > - rebased on master
> > > > - filled with zeroed buffer [Max]
> > > > - used rbd_writesame() only when we can disable the discard of zeroed
> > > > buffers
> > > > - added 'since: 4.2' in qapi/block-core.json [Max]
> > > > - used buffer as large as the "stripe unit"
> > > > ---
> > > > block/rbd.c | 202 ++++++++++++++++++++++++++++++++++++++++---
> > > > qapi/block-core.json | 5 +-
> > > > 2 files changed, 192 insertions(+), 15 deletions(-)
> > > >
> > > > diff --git a/block/rbd.c b/block/rbd.c
> > > > index 59757b3120..d923a5a26c 100644
> > > > --- a/block/rbd.c
> > > > +++ b/block/rbd.c
> > > > @@ -64,6 +64,7 @@
> > > > #define OBJ_MAX_SIZE (1UL << OBJ_DEFAULT_OBJ_ORDER)
> > > >
> > > > #define RBD_MAX_SNAPS 100
> > > > +#define RBD_DEFAULT_CONCURRENT_OPS 10
> > > >
> > > > /* The LIBRBD_SUPPORTS_IOVEC is defined in librbd.h */
> > > > #ifdef LIBRBD_SUPPORTS_IOVEC
> > > > @@ -104,6 +105,7 @@ typedef struct BDRVRBDState {
> > > > char *image_name;
> > > > char *snap;
> > > > uint64_t image_size;
> > > > + bool ws_zero_supported; /* rbd_writesame() supports zeroed buffers */
> > > > } BDRVRBDState;
> > > >
> > > > static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
> > > > @@ -333,6 +335,155 @@ static void qemu_rbd_memset(RADOSCB *rcb, int64_t offs)
> > > > }
> > > > }
> > > >
> > > > +static int qemu_rbd_get_max_concurrent_ops(rados_t cluster)
> > > > +{
> > > > + char buf[16];
> > > > + int ret, max_concurrent_ops;
> > > > +
> > > > + ret = rados_conf_get(cluster, "rbd_concurrent_management_ops", buf,
> > > > + sizeof(buf));
> > > > + if (ret < 0) {
> > > > + return RBD_DEFAULT_CONCURRENT_OPS;
> > > > + }
> > > > +
> > > > + ret = qemu_strtoi(buf, NULL, 10, &max_concurrent_ops);
> > > > + if (ret < 0) {
> > > > + return RBD_DEFAULT_CONCURRENT_OPS;
> > > > + }
> > > > +
> > > > + return max_concurrent_ops;
> > > > +}
> > > > +
> > > > +static int qemu_rbd_do_truncate(rados_t cluster, rbd_image_t image,
> > > > + int64_t offset, PreallocMode prealloc,
> > > > + bool ws_zero_supported, Error **errp)
> > > > +{
> > > > + uint64_t current_length;
> > > > + char *buf = NULL;
> > > > + int ret;
> > > > +
> > > > + ret = rbd_get_size(image, ¤t_length);
> > > > + if (ret < 0) {
> > > > + error_setg_errno(errp, -ret, "Failed to get file length");
> > > > + goto out;
> > > > + }
> > > > +
> > > > + if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
> > > > + error_setg(errp, "Cannot use preallocation for shrinking files");
> > > > + ret = -ENOTSUP;
> > > > + goto out;
> > > > + }
> > > > +
> > > > + switch (prealloc) {
> > > > + case PREALLOC_MODE_FULL: {
> > > > + uint64_t buf_size, current_offset = current_length;
> > > > + ssize_t bytes;
> > > > +
> > > > + ret = rbd_get_stripe_unit(image, &buf_size);
> > > > + if (ret < 0) {
> > > > + error_setg_errno(errp, -ret, "Failed to get stripe unit");
> > > > + goto out;
> > > > + }
> > > > +
> > > > + ret = rbd_resize(image, offset);
> > > > + if (ret < 0) {
> > > > + error_setg_errno(errp, -ret, "Failed to resize file");
> > > > + goto out;
> > > > + }
> > > > +
> > > > + buf = g_malloc0(buf_size);
> > > > +
> > > > +#ifdef LIBRBD_SUPPORTS_WRITESAME
> > > > + if (ws_zero_supported) {
> > > > + uint64_t writesame_max_size;
> > > > + int max_concurrent_ops;
> > > > +
> > > > + max_concurrent_ops = qemu_rbd_get_max_concurrent_ops(cluster);
> > > > + /*
> > > > + * We limit the rbd_writesame() size to avoid to spawn more then
> > > > + * 'rbd_concurrent_management_ops' concurrent operations.
> > > > + */
> > > > + writesame_max_size = MIN(buf_size * max_concurrent_ops, INT_MAX);
> > >
> > > In the most efficient world, the 'buf_size' would be some small, fixed
> > > power of 2 value (like 512 bytes) since there isn't much need to send
> > > extra zeroes. You would then want to writesame the full stripe period
> > > (if possible), where a stripe period is the data block object size
> > > (defaults to 4MiB and is availble via 'rbd_stat') * the stripe count.
> > > In this case, the stripe count becomes the number of in-flight IOs.
> > > Therefore, you could substitute its value w/ the max_concurrent_ops to
> > > ensure you are issuing exactly max_concurrent_ops IOs per
> > > rbd_writesame call.
> > >
> >
> > Initially, I had a fixed buffer size to 4 KiB, but I noted that, when
> > we didn't use writesame, the rbd_write() was very slow, so I used the
> > stripe unit as a buffer size.
> >
> > Do you think is better to have a small buffer (512 byte) when we use
> > writesame or a 'stripe unit' buffer when we can't use it?
>
> I'd use a small buffer for rbd_writesame and then just reallocate the
My idea was to allocate a small buffer for rbd_writesame and use the
same to write the remaining bytes that should be a few.
If the buffer was not allocated (so we didn't use the rbd_writesame),
I'll allocate the big one:
if (ws_zero_supported) {
buf_size = 512;
buf = g_malloc0(buf_size);
...
}
if (!buf) {
buf_size = object_size * max_concurrent_ops;
buf = g_malloc0(buf_size);
}
while (current_offset < offset) {
bytes = rbd_write(...)
...
}
> buffer to a larger size for "rbd_write". It would be most efficient to
> allocate a "object size * max concurrent ops" -sized buffer (up to
Why "object size * max concurrent ops" and not
"stripe_unit * max concurrent ops"?
IIUC stripe_unit can be smaller than object size.
> some reasonable maximum) for the standard rbd_write. Just make sure
> your "rbd_writes" offsets / length is aligned to the stripe period for
> the most efficient IO (i.e. the initial write might be smaller than
> the stripe period if the starting offset is unaligned).
>
Okay, I'll do the first small write to align the next writes to the
stripe period (obj size * stripe_count).
> > > > +
> > > > + while (offset - current_offset > buf_size) {
> > > > + bytes = MIN(offset - current_offset, writesame_max_size);
> > > > + /*
> > > > + * rbd_writesame() supports only request where the size of the
> > > > + * operation is multiple of buffer size.
> > > > + */
> > > > + bytes -= bytes % buf_size;
> > > > +
> > > > + bytes = rbd_writesame(image, current_offset, bytes, buf,
> > > > + buf_size, 0);
> > >
> > > If the RBD in-memory cache is enabled during this operation, the
> > > writesame will effectively just be turned into a write. Therefore,
> > > when pre-allocating, you will want to disable the cache.
> > >
> >
> > During the creation, when preallocation is often used, we disable the cache:
> >
> > static int qemu_rbd_do_create(BlockdevCreateOptions *options,
> > const char *keypairs, const char *password_secret,
> > Error **errp)
> > {
> > ...
> >
> > ret = qemu_rbd_connect(&cluster, &io_ctx, opts->location, false, keypairs,
> > ^^ cache param
> > ...
> > }
> >
> >
> > Do you think I should disable it in any case during the preallocation?
>
> Assuming you can grow an image w/ full preallocation, I would
> definitely want to ensure that the cache is disabled since otherwise
> you would just be performing regular (non-offloaded) writes.
>
Yes, make sense, I'll disable the cache.
> >
> >
> > > > + if (bytes < 0) {
> > > > + ret = bytes;
> > > > + error_setg_errno(errp, -ret,
> > > > + "Failed to write for preallocation");
> > > > + goto out;
> > > > + }
> > > > +
> > > > + current_offset += bytes;
> > > > + }
> > > > + }
> > > > +#endif /* LIBRBD_SUPPORTS_WRITESAME */
> > > > +
> > > > + while (current_offset < offset) {
> > > > + bytes = rbd_write(image, current_offset,
> > > > + MIN(offset - current_offset, buf_size), buf);
> > > > + if (bytes < 0) {
> > > > + ret = bytes;
> > > > + error_setg_errno(errp, -ret,
> > > > + "Failed to write for preallocation");
> > > > + goto out;
> > > > + }
> > > > +
> > > > + current_offset += bytes;
> > > > + }
> > > > +
> > > > + ret = rbd_flush(image);
> > > > + if (ret < 0) {
> > > > + error_setg_errno(errp, -ret, "Failed to flush the file");
> > > > + goto out;
> > > > + }
> > > > +
> > > > + break;
> > > > + }
> > > > + case PREALLOC_MODE_OFF:
> > > > + ret = rbd_resize(image, offset);
> > >
> > > I'm not familiar enough w/ the QEMU block code, but why would the
> > > PREALLOC_MODE_FULL case not need to resize the image?
> >
> > PREALLOC_MODE_FULL need too, I did it just before the g_malloc0() in
> > this patch :-)
>
> Sorry I missed it. Would it make more sense to just do it before the
> switch statement so that you don't duplicate the code and resulting
> error handling? I guess just validate that the prealloc mode is
> supported before issuing the resize.
>
Sure, it's more robust in this way.
Thanks,
Stefano
On Fri, Jul 26, 2019 at 4:48 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> On Thu, Jul 25, 2019 at 09:30:30AM -0400, Jason Dillaman wrote:
> > On Thu, Jul 25, 2019 at 4:13 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
> > >
> > > On Wed, Jul 24, 2019 at 01:48:42PM -0400, Jason Dillaman wrote:
> > > > On Tue, Jul 23, 2019 at 3:13 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
> > > > >
> > > > > This patch adds the support of preallocation (off/full) for the RBD
> > > > > block driver.
> > > > > If rbd_writesame() is available and supports zeroed buffers, we use
> > > > > it to quickly fill the image when full preallocation is required.
> > > > >
> > > > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> > > > > ---
> > > > > v3:
> > > > > - rebased on master
> > > > > - filled with zeroed buffer [Max]
> > > > > - used rbd_writesame() only when we can disable the discard of zeroed
> > > > > buffers
> > > > > - added 'since: 4.2' in qapi/block-core.json [Max]
> > > > > - used buffer as large as the "stripe unit"
> > > > > ---
> > > > > block/rbd.c | 202 ++++++++++++++++++++++++++++++++++++++++---
> > > > > qapi/block-core.json | 5 +-
> > > > > 2 files changed, 192 insertions(+), 15 deletions(-)
> > > > >
> > > > > diff --git a/block/rbd.c b/block/rbd.c
> > > > > index 59757b3120..d923a5a26c 100644
> > > > > --- a/block/rbd.c
> > > > > +++ b/block/rbd.c
> > > > > @@ -64,6 +64,7 @@
> > > > > #define OBJ_MAX_SIZE (1UL << OBJ_DEFAULT_OBJ_ORDER)
> > > > >
> > > > > #define RBD_MAX_SNAPS 100
> > > > > +#define RBD_DEFAULT_CONCURRENT_OPS 10
> > > > >
> > > > > /* The LIBRBD_SUPPORTS_IOVEC is defined in librbd.h */
> > > > > #ifdef LIBRBD_SUPPORTS_IOVEC
> > > > > @@ -104,6 +105,7 @@ typedef struct BDRVRBDState {
> > > > > char *image_name;
> > > > > char *snap;
> > > > > uint64_t image_size;
> > > > > + bool ws_zero_supported; /* rbd_writesame() supports zeroed buffers */
> > > > > } BDRVRBDState;
> > > > >
> > > > > static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
> > > > > @@ -333,6 +335,155 @@ static void qemu_rbd_memset(RADOSCB *rcb, int64_t offs)
> > > > > }
> > > > > }
> > > > >
> > > > > +static int qemu_rbd_get_max_concurrent_ops(rados_t cluster)
> > > > > +{
> > > > > + char buf[16];
> > > > > + int ret, max_concurrent_ops;
> > > > > +
> > > > > + ret = rados_conf_get(cluster, "rbd_concurrent_management_ops", buf,
> > > > > + sizeof(buf));
> > > > > + if (ret < 0) {
> > > > > + return RBD_DEFAULT_CONCURRENT_OPS;
> > > > > + }
> > > > > +
> > > > > + ret = qemu_strtoi(buf, NULL, 10, &max_concurrent_ops);
> > > > > + if (ret < 0) {
> > > > > + return RBD_DEFAULT_CONCURRENT_OPS;
> > > > > + }
> > > > > +
> > > > > + return max_concurrent_ops;
> > > > > +}
> > > > > +
> > > > > +static int qemu_rbd_do_truncate(rados_t cluster, rbd_image_t image,
> > > > > + int64_t offset, PreallocMode prealloc,
> > > > > + bool ws_zero_supported, Error **errp)
> > > > > +{
> > > > > + uint64_t current_length;
> > > > > + char *buf = NULL;
> > > > > + int ret;
> > > > > +
> > > > > + ret = rbd_get_size(image, ¤t_length);
> > > > > + if (ret < 0) {
> > > > > + error_setg_errno(errp, -ret, "Failed to get file length");
> > > > > + goto out;
> > > > > + }
> > > > > +
> > > > > + if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
> > > > > + error_setg(errp, "Cannot use preallocation for shrinking files");
> > > > > + ret = -ENOTSUP;
> > > > > + goto out;
> > > > > + }
> > > > > +
> > > > > + switch (prealloc) {
> > > > > + case PREALLOC_MODE_FULL: {
> > > > > + uint64_t buf_size, current_offset = current_length;
> > > > > + ssize_t bytes;
> > > > > +
> > > > > + ret = rbd_get_stripe_unit(image, &buf_size);
> > > > > + if (ret < 0) {
> > > > > + error_setg_errno(errp, -ret, "Failed to get stripe unit");
> > > > > + goto out;
> > > > > + }
> > > > > +
> > > > > + ret = rbd_resize(image, offset);
> > > > > + if (ret < 0) {
> > > > > + error_setg_errno(errp, -ret, "Failed to resize file");
> > > > > + goto out;
> > > > > + }
> > > > > +
> > > > > + buf = g_malloc0(buf_size);
> > > > > +
> > > > > +#ifdef LIBRBD_SUPPORTS_WRITESAME
> > > > > + if (ws_zero_supported) {
> > > > > + uint64_t writesame_max_size;
> > > > > + int max_concurrent_ops;
> > > > > +
> > > > > + max_concurrent_ops = qemu_rbd_get_max_concurrent_ops(cluster);
> > > > > + /*
> > > > > + * We limit the rbd_writesame() size to avoid to spawn more then
> > > > > + * 'rbd_concurrent_management_ops' concurrent operations.
> > > > > + */
> > > > > + writesame_max_size = MIN(buf_size * max_concurrent_ops, INT_MAX);
> > > >
> > > > In the most efficient world, the 'buf_size' would be some small, fixed
> > > > power of 2 value (like 512 bytes) since there isn't much need to send
> > > > extra zeroes. You would then want to writesame the full stripe period
> > > > (if possible), where a stripe period is the data block object size
> > > > (defaults to 4MiB and is availble via 'rbd_stat') * the stripe count.
> > > > In this case, the stripe count becomes the number of in-flight IOs.
> > > > Therefore, you could substitute its value w/ the max_concurrent_ops to
> > > > ensure you are issuing exactly max_concurrent_ops IOs per
> > > > rbd_writesame call.
> > > >
> > >
> > > Initially, I had a fixed buffer size to 4 KiB, but I noted that, when
> > > we didn't use writesame, the rbd_write() was very slow, so I used the
> > > stripe unit as a buffer size.
> > >
> > > Do you think is better to have a small buffer (512 byte) when we use
> > > writesame or a 'stripe unit' buffer when we can't use it?
> >
> > I'd use a small buffer for rbd_writesame and then just reallocate the
>
> My idea was to allocate a small buffer for rbd_writesame and use the
> same to write the remaining bytes that should be a few.
> If the buffer was not allocated (so we didn't use the rbd_writesame),
> I'll allocate the big one:
>
> if (ws_zero_supported) {
> buf_size = 512;
> buf = g_malloc0(buf_size);
> ...
> }
>
> if (!buf) {
> buf_size = object_size * max_concurrent_ops;
> buf = g_malloc0(buf_size);
> }
>
> while (current_offset < offset) {
> bytes = rbd_write(...)
> ...
> }
>
> > buffer to a larger size for "rbd_write". It would be most efficient to
> > allocate a "object size * max concurrent ops" -sized buffer (up to
>
> Why "object size * max concurrent ops" and not
> "stripe_unit * max concurrent ops"?
> IIUC stripe_unit can be smaller than object size.
Correct, stripe unit *must* be smaller than the object size (and both
are powers of two). However, it's more efficient to send fewer larger
writes to a backing object than sending more small writes --
especially in the case of writesame where you don't have the network
overhead of transferring a large zeroed buffer. Replacing the full
backing object is even more efficient since it will just need to
perform a single backing disk allocation that will be continuous
instead of fragmented.
> > some reasonable maximum) for the standard rbd_write. Just make sure
> > your "rbd_writes" offsets / length is aligned to the stripe period for
> > the most efficient IO (i.e. the initial write might be smaller than
> > the stripe period if the starting offset is unaligned).
> >
>
> Okay, I'll do the first small write to align the next writes to the
> stripe period (obj size * stripe_count).
>
> > > > > +
> > > > > + while (offset - current_offset > buf_size) {
> > > > > + bytes = MIN(offset - current_offset, writesame_max_size);
> > > > > + /*
> > > > > + * rbd_writesame() supports only request where the size of the
> > > > > + * operation is multiple of buffer size.
> > > > > + */
> > > > > + bytes -= bytes % buf_size;
> > > > > +
> > > > > + bytes = rbd_writesame(image, current_offset, bytes, buf,
> > > > > + buf_size, 0);
> > > >
> > > > If the RBD in-memory cache is enabled during this operation, the
> > > > writesame will effectively just be turned into a write. Therefore,
> > > > when pre-allocating, you will want to disable the cache.
> > > >
> > >
> > > During the creation, when preallocation is often used, we disable the cache:
> > >
> > > static int qemu_rbd_do_create(BlockdevCreateOptions *options,
> > > const char *keypairs, const char *password_secret,
> > > Error **errp)
> > > {
> > > ...
> > >
> > > ret = qemu_rbd_connect(&cluster, &io_ctx, opts->location, false, keypairs,
> > > ^^ cache param
> > > ...
> > > }
> > >
> > >
> > > Do you think I should disable it in any case during the preallocation?
> >
> > Assuming you can grow an image w/ full preallocation, I would
> > definitely want to ensure that the cache is disabled since otherwise
> > you would just be performing regular (non-offloaded) writes.
> >
>
> Yes, make sense, I'll disable the cache.
>
> > >
> > >
> > > > > + if (bytes < 0) {
> > > > > + ret = bytes;
> > > > > + error_setg_errno(errp, -ret,
> > > > > + "Failed to write for preallocation");
> > > > > + goto out;
> > > > > + }
> > > > > +
> > > > > + current_offset += bytes;
> > > > > + }
> > > > > + }
> > > > > +#endif /* LIBRBD_SUPPORTS_WRITESAME */
> > > > > +
> > > > > + while (current_offset < offset) {
> > > > > + bytes = rbd_write(image, current_offset,
> > > > > + MIN(offset - current_offset, buf_size), buf);
> > > > > + if (bytes < 0) {
> > > > > + ret = bytes;
> > > > > + error_setg_errno(errp, -ret,
> > > > > + "Failed to write for preallocation");
> > > > > + goto out;
> > > > > + }
> > > > > +
> > > > > + current_offset += bytes;
> > > > > + }
> > > > > +
> > > > > + ret = rbd_flush(image);
> > > > > + if (ret < 0) {
> > > > > + error_setg_errno(errp, -ret, "Failed to flush the file");
> > > > > + goto out;
> > > > > + }
> > > > > +
> > > > > + break;
> > > > > + }
> > > > > + case PREALLOC_MODE_OFF:
> > > > > + ret = rbd_resize(image, offset);
> > > >
> > > > I'm not familiar enough w/ the QEMU block code, but why would the
> > > > PREALLOC_MODE_FULL case not need to resize the image?
> > >
> > > PREALLOC_MODE_FULL need too, I did it just before the g_malloc0() in
> > > this patch :-)
> >
> > Sorry I missed it. Would it make more sense to just do it before the
> > switch statement so that you don't duplicate the code and resulting
> > error handling? I guess just validate that the prealloc mode is
> > supported before issuing the resize.
> >
>
> Sure, it's more robust in this way.
>
> Thanks,
> Stefano
--
Jason
On Fri, Jul 26, 2019 at 08:46:56AM -0400, Jason Dillaman wrote:
> On Fri, Jul 26, 2019 at 4:48 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
> >
> > On Thu, Jul 25, 2019 at 09:30:30AM -0400, Jason Dillaman wrote:
> > > On Thu, Jul 25, 2019 at 4:13 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
> > > >
> > > > On Wed, Jul 24, 2019 at 01:48:42PM -0400, Jason Dillaman wrote:
> > > > > On Tue, Jul 23, 2019 at 3:13 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
> > > > > >
> > > > > > This patch adds the support of preallocation (off/full) for the RBD
> > > > > > block driver.
> > > > > > If rbd_writesame() is available and supports zeroed buffers, we use
> > > > > > it to quickly fill the image when full preallocation is required.
> > > > > >
> > > > > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> > > > > > ---
> > > > > > v3:
> > > > > > - rebased on master
> > > > > > - filled with zeroed buffer [Max]
> > > > > > - used rbd_writesame() only when we can disable the discard of zeroed
> > > > > > buffers
> > > > > > - added 'since: 4.2' in qapi/block-core.json [Max]
> > > > > > - used buffer as large as the "stripe unit"
> > > > > > ---
> > > > > > block/rbd.c | 202 ++++++++++++++++++++++++++++++++++++++++---
> > > > > > qapi/block-core.json | 5 +-
> > > > > > 2 files changed, 192 insertions(+), 15 deletions(-)
> > > > > >
> > > > > > diff --git a/block/rbd.c b/block/rbd.c
> > > > > > index 59757b3120..d923a5a26c 100644
> > > > > > --- a/block/rbd.c
> > > > > > +++ b/block/rbd.c
> > > > > > @@ -64,6 +64,7 @@
> > > > > > #define OBJ_MAX_SIZE (1UL << OBJ_DEFAULT_OBJ_ORDER)
> > > > > >
> > > > > > #define RBD_MAX_SNAPS 100
> > > > > > +#define RBD_DEFAULT_CONCURRENT_OPS 10
> > > > > >
> > > > > > /* The LIBRBD_SUPPORTS_IOVEC is defined in librbd.h */
> > > > > > #ifdef LIBRBD_SUPPORTS_IOVEC
> > > > > > @@ -104,6 +105,7 @@ typedef struct BDRVRBDState {
> > > > > > char *image_name;
> > > > > > char *snap;
> > > > > > uint64_t image_size;
> > > > > > + bool ws_zero_supported; /* rbd_writesame() supports zeroed buffers */
> > > > > > } BDRVRBDState;
> > > > > >
> > > > > > static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
> > > > > > @@ -333,6 +335,155 @@ static void qemu_rbd_memset(RADOSCB *rcb, int64_t offs)
> > > > > > }
> > > > > > }
> > > > > >
> > > > > > +static int qemu_rbd_get_max_concurrent_ops(rados_t cluster)
> > > > > > +{
> > > > > > + char buf[16];
> > > > > > + int ret, max_concurrent_ops;
> > > > > > +
> > > > > > + ret = rados_conf_get(cluster, "rbd_concurrent_management_ops", buf,
> > > > > > + sizeof(buf));
> > > > > > + if (ret < 0) {
> > > > > > + return RBD_DEFAULT_CONCURRENT_OPS;
> > > > > > + }
> > > > > > +
> > > > > > + ret = qemu_strtoi(buf, NULL, 10, &max_concurrent_ops);
> > > > > > + if (ret < 0) {
> > > > > > + return RBD_DEFAULT_CONCURRENT_OPS;
> > > > > > + }
> > > > > > +
> > > > > > + return max_concurrent_ops;
> > > > > > +}
> > > > > > +
> > > > > > +static int qemu_rbd_do_truncate(rados_t cluster, rbd_image_t image,
> > > > > > + int64_t offset, PreallocMode prealloc,
> > > > > > + bool ws_zero_supported, Error **errp)
> > > > > > +{
> > > > > > + uint64_t current_length;
> > > > > > + char *buf = NULL;
> > > > > > + int ret;
> > > > > > +
> > > > > > + ret = rbd_get_size(image, ¤t_length);
> > > > > > + if (ret < 0) {
> > > > > > + error_setg_errno(errp, -ret, "Failed to get file length");
> > > > > > + goto out;
> > > > > > + }
> > > > > > +
> > > > > > + if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
> > > > > > + error_setg(errp, "Cannot use preallocation for shrinking files");
> > > > > > + ret = -ENOTSUP;
> > > > > > + goto out;
> > > > > > + }
> > > > > > +
> > > > > > + switch (prealloc) {
> > > > > > + case PREALLOC_MODE_FULL: {
> > > > > > + uint64_t buf_size, current_offset = current_length;
> > > > > > + ssize_t bytes;
> > > > > > +
> > > > > > + ret = rbd_get_stripe_unit(image, &buf_size);
> > > > > > + if (ret < 0) {
> > > > > > + error_setg_errno(errp, -ret, "Failed to get stripe unit");
> > > > > > + goto out;
> > > > > > + }
> > > > > > +
> > > > > > + ret = rbd_resize(image, offset);
> > > > > > + if (ret < 0) {
> > > > > > + error_setg_errno(errp, -ret, "Failed to resize file");
> > > > > > + goto out;
> > > > > > + }
> > > > > > +
> > > > > > + buf = g_malloc0(buf_size);
> > > > > > +
> > > > > > +#ifdef LIBRBD_SUPPORTS_WRITESAME
> > > > > > + if (ws_zero_supported) {
> > > > > > + uint64_t writesame_max_size;
> > > > > > + int max_concurrent_ops;
> > > > > > +
> > > > > > + max_concurrent_ops = qemu_rbd_get_max_concurrent_ops(cluster);
> > > > > > + /*
> > > > > > + * We limit the rbd_writesame() size to avoid to spawn more then
> > > > > > + * 'rbd_concurrent_management_ops' concurrent operations.
> > > > > > + */
> > > > > > + writesame_max_size = MIN(buf_size * max_concurrent_ops, INT_MAX);
> > > > >
> > > > > In the most efficient world, the 'buf_size' would be some small, fixed
> > > > > power of 2 value (like 512 bytes) since there isn't much need to send
> > > > > extra zeroes. You would then want to writesame the full stripe period
> > > > > (if possible), where a stripe period is the data block object size
> > > > > (defaults to 4MiB and is availble via 'rbd_stat') * the stripe count.
> > > > > In this case, the stripe count becomes the number of in-flight IOs.
> > > > > Therefore, you could substitute its value w/ the max_concurrent_ops to
> > > > > ensure you are issuing exactly max_concurrent_ops IOs per
> > > > > rbd_writesame call.
> > > > >
> > > >
> > > > Initially, I had a fixed buffer size to 4 KiB, but I noted that, when
> > > > we didn't use writesame, the rbd_write() was very slow, so I used the
> > > > stripe unit as a buffer size.
> > > >
> > > > Do you think is better to have a small buffer (512 byte) when we use
> > > > writesame or a 'stripe unit' buffer when we can't use it?
> > >
> > > I'd use a small buffer for rbd_writesame and then just reallocate the
> >
> > My idea was to allocate a small buffer for rbd_writesame and use the
> > same to write the remaining bytes that should be a few.
> > If the buffer was not allocated (so we didn't use the rbd_writesame),
> > I'll allocate the big one:
> >
> > if (ws_zero_supported) {
> > buf_size = 512;
> > buf = g_malloc0(buf_size);
> > ...
> > }
> >
> > if (!buf) {
> > buf_size = object_size * max_concurrent_ops;
> > buf = g_malloc0(buf_size);
> > }
> >
> > while (current_offset < offset) {
> > bytes = rbd_write(...)
> > ...
> > }
> >
> > > buffer to a larger size for "rbd_write". It would be most efficient to
> > > allocate a "object size * max concurrent ops" -sized buffer (up to
> >
> > Why "object size * max concurrent ops" and not
> > "stripe_unit * max concurrent ops"?
> > IIUC stripe_unit can be smaller than object size.
>
> Correct, stripe unit *must* be smaller than the object size (and both
> are powers of two). However, it's more efficient to send fewer larger
> writes to a backing object than sending more small writes --
> especially in the case of writesame where you don't have the network
> overhead of transferring a large zeroed buffer. Replacing the full
> backing object is even more efficient since it will just need to
> perform a single backing disk allocation that will be continuous
> instead of fragmented.
>
Okay, so IIUC I should do the following:
- if we can use rbd_writesame
~ allocates a buffer of 512 bytes
~ writes "object size * max concurrent ops" bytes per call
- if we use rbd_write
~ allocates a buffer of "object size * max concurrent ops" bytes
~ writes the entire buffer per call (aligning to the stripe unit)
Is that correct?
Thanks,
Stefano
On Mon, Jul 29, 2019 at 5:40 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> On Fri, Jul 26, 2019 at 08:46:56AM -0400, Jason Dillaman wrote:
> > On Fri, Jul 26, 2019 at 4:48 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
> > >
> > > On Thu, Jul 25, 2019 at 09:30:30AM -0400, Jason Dillaman wrote:
> > > > On Thu, Jul 25, 2019 at 4:13 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
> > > > >
> > > > > On Wed, Jul 24, 2019 at 01:48:42PM -0400, Jason Dillaman wrote:
> > > > > > On Tue, Jul 23, 2019 at 3:13 AM Stefano Garzarella <sgarzare@redhat.com> wrote:
> > > > > > >
> > > > > > > This patch adds the support of preallocation (off/full) for the RBD
> > > > > > > block driver.
> > > > > > > If rbd_writesame() is available and supports zeroed buffers, we use
> > > > > > > it to quickly fill the image when full preallocation is required.
> > > > > > >
> > > > > > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> > > > > > > ---
> > > > > > > v3:
> > > > > > > - rebased on master
> > > > > > > - filled with zeroed buffer [Max]
> > > > > > > - used rbd_writesame() only when we can disable the discard of zeroed
> > > > > > > buffers
> > > > > > > - added 'since: 4.2' in qapi/block-core.json [Max]
> > > > > > > - used buffer as large as the "stripe unit"
> > > > > > > ---
> > > > > > > block/rbd.c | 202 ++++++++++++++++++++++++++++++++++++++++---
> > > > > > > qapi/block-core.json | 5 +-
> > > > > > > 2 files changed, 192 insertions(+), 15 deletions(-)
> > > > > > >
> > > > > > > diff --git a/block/rbd.c b/block/rbd.c
> > > > > > > index 59757b3120..d923a5a26c 100644
> > > > > > > --- a/block/rbd.c
> > > > > > > +++ b/block/rbd.c
> > > > > > > @@ -64,6 +64,7 @@
> > > > > > > #define OBJ_MAX_SIZE (1UL << OBJ_DEFAULT_OBJ_ORDER)
> > > > > > >
> > > > > > > #define RBD_MAX_SNAPS 100
> > > > > > > +#define RBD_DEFAULT_CONCURRENT_OPS 10
> > > > > > >
> > > > > > > /* The LIBRBD_SUPPORTS_IOVEC is defined in librbd.h */
> > > > > > > #ifdef LIBRBD_SUPPORTS_IOVEC
> > > > > > > @@ -104,6 +105,7 @@ typedef struct BDRVRBDState {
> > > > > > > char *image_name;
> > > > > > > char *snap;
> > > > > > > uint64_t image_size;
> > > > > > > + bool ws_zero_supported; /* rbd_writesame() supports zeroed buffers */
> > > > > > > } BDRVRBDState;
> > > > > > >
> > > > > > > static int qemu_rbd_connect(rados_t *cluster, rados_ioctx_t *io_ctx,
> > > > > > > @@ -333,6 +335,155 @@ static void qemu_rbd_memset(RADOSCB *rcb, int64_t offs)
> > > > > > > }
> > > > > > > }
> > > > > > >
> > > > > > > +static int qemu_rbd_get_max_concurrent_ops(rados_t cluster)
> > > > > > > +{
> > > > > > > + char buf[16];
> > > > > > > + int ret, max_concurrent_ops;
> > > > > > > +
> > > > > > > + ret = rados_conf_get(cluster, "rbd_concurrent_management_ops", buf,
> > > > > > > + sizeof(buf));
> > > > > > > + if (ret < 0) {
> > > > > > > + return RBD_DEFAULT_CONCURRENT_OPS;
> > > > > > > + }
> > > > > > > +
> > > > > > > + ret = qemu_strtoi(buf, NULL, 10, &max_concurrent_ops);
> > > > > > > + if (ret < 0) {
> > > > > > > + return RBD_DEFAULT_CONCURRENT_OPS;
> > > > > > > + }
> > > > > > > +
> > > > > > > + return max_concurrent_ops;
> > > > > > > +}
> > > > > > > +
> > > > > > > +static int qemu_rbd_do_truncate(rados_t cluster, rbd_image_t image,
> > > > > > > + int64_t offset, PreallocMode prealloc,
> > > > > > > + bool ws_zero_supported, Error **errp)
> > > > > > > +{
> > > > > > > + uint64_t current_length;
> > > > > > > + char *buf = NULL;
> > > > > > > + int ret;
> > > > > > > +
> > > > > > > + ret = rbd_get_size(image, ¤t_length);
> > > > > > > + if (ret < 0) {
> > > > > > > + error_setg_errno(errp, -ret, "Failed to get file length");
> > > > > > > + goto out;
> > > > > > > + }
> > > > > > > +
> > > > > > > + if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
> > > > > > > + error_setg(errp, "Cannot use preallocation for shrinking files");
> > > > > > > + ret = -ENOTSUP;
> > > > > > > + goto out;
> > > > > > > + }
> > > > > > > +
> > > > > > > + switch (prealloc) {
> > > > > > > + case PREALLOC_MODE_FULL: {
> > > > > > > + uint64_t buf_size, current_offset = current_length;
> > > > > > > + ssize_t bytes;
> > > > > > > +
> > > > > > > + ret = rbd_get_stripe_unit(image, &buf_size);
> > > > > > > + if (ret < 0) {
> > > > > > > + error_setg_errno(errp, -ret, "Failed to get stripe unit");
> > > > > > > + goto out;
> > > > > > > + }
> > > > > > > +
> > > > > > > + ret = rbd_resize(image, offset);
> > > > > > > + if (ret < 0) {
> > > > > > > + error_setg_errno(errp, -ret, "Failed to resize file");
> > > > > > > + goto out;
> > > > > > > + }
> > > > > > > +
> > > > > > > + buf = g_malloc0(buf_size);
> > > > > > > +
> > > > > > > +#ifdef LIBRBD_SUPPORTS_WRITESAME
> > > > > > > + if (ws_zero_supported) {
> > > > > > > + uint64_t writesame_max_size;
> > > > > > > + int max_concurrent_ops;
> > > > > > > +
> > > > > > > + max_concurrent_ops = qemu_rbd_get_max_concurrent_ops(cluster);
> > > > > > > + /*
> > > > > > > + * We limit the rbd_writesame() size to avoid to spawn more then
> > > > > > > + * 'rbd_concurrent_management_ops' concurrent operations.
> > > > > > > + */
> > > > > > > + writesame_max_size = MIN(buf_size * max_concurrent_ops, INT_MAX);
> > > > > >
> > > > > > In the most efficient world, the 'buf_size' would be some small, fixed
> > > > > > power of 2 value (like 512 bytes) since there isn't much need to send
> > > > > > extra zeroes. You would then want to writesame the full stripe period
> > > > > > (if possible), where a stripe period is the data block object size
> > > > > > (defaults to 4MiB and is availble via 'rbd_stat') * the stripe count.
> > > > > > In this case, the stripe count becomes the number of in-flight IOs.
> > > > > > Therefore, you could substitute its value w/ the max_concurrent_ops to
> > > > > > ensure you are issuing exactly max_concurrent_ops IOs per
> > > > > > rbd_writesame call.
> > > > > >
> > > > >
> > > > > Initially, I had a fixed buffer size to 4 KiB, but I noted that, when
> > > > > we didn't use writesame, the rbd_write() was very slow, so I used the
> > > > > stripe unit as a buffer size.
> > > > >
> > > > > Do you think is better to have a small buffer (512 byte) when we use
> > > > > writesame or a 'stripe unit' buffer when we can't use it?
> > > >
> > > > I'd use a small buffer for rbd_writesame and then just reallocate the
> > >
> > > My idea was to allocate a small buffer for rbd_writesame and use the
> > > same to write the remaining bytes that should be a few.
> > > If the buffer was not allocated (so we didn't use the rbd_writesame),
> > > I'll allocate the big one:
> > >
> > > if (ws_zero_supported) {
> > > buf_size = 512;
> > > buf = g_malloc0(buf_size);
> > > ...
> > > }
> > >
> > > if (!buf) {
> > > buf_size = object_size * max_concurrent_ops;
> > > buf = g_malloc0(buf_size);
> > > }
> > >
> > > while (current_offset < offset) {
> > > bytes = rbd_write(...)
> > > ...
> > > }
> > >
> > > > buffer to a larger size for "rbd_write". It would be most efficient to
> > > > allocate a "object size * max concurrent ops" -sized buffer (up to
> > >
> > > Why "object size * max concurrent ops" and not
> > > "stripe_unit * max concurrent ops"?
> > > IIUC stripe_unit can be smaller than object size.
> >
> > Correct, stripe unit *must* be smaller than the object size (and both
> > are powers of two). However, it's more efficient to send fewer larger
> > writes to a backing object than sending more small writes --
> > especially in the case of writesame where you don't have the network
> > overhead of transferring a large zeroed buffer. Replacing the full
> > backing object is even more efficient since it will just need to
> > perform a single backing disk allocation that will be continuous
> > instead of fragmented.
> >
>
> Okay, so IIUC I should do the following:
> - if we can use rbd_writesame
> ~ allocates a buffer of 512 bytes
> ~ writes "object size * max concurrent ops" bytes per call
> - if we use rbd_write
> ~ allocates a buffer of "object size * max concurrent ops" bytes
> ~ writes the entire buffer per call (aligning to the stripe unit)
>
> Is that correct?
Yes, that is correct.
> Thanks,
> Stefano
--
Jason
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