From: Hao Xiang <hao.xiang@bytedance.com>
1. Add zero_pages field in MultiFDPacket_t.
2. Implements the zero page detection and handling on the multifd
threads for non-compression, zlib and zstd compression backends.
3. Added a new value 'multifd' in ZeroPageDetection enumeration.
4. Adds zero page counters and updates multifd send/receive tracing
format to track the newly added counters.
Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240311180015.3359271-5-hao.xiang@linux.dev
Signed-off-by: Peter Xu <peterx@redhat.com>
---
qapi/migration.json | 7 ++-
migration/multifd.h | 23 +++++++-
hw/core/qdev-properties-system.c | 2 +-
migration/multifd-zero-page.c | 87 ++++++++++++++++++++++++++++++
migration/multifd-zlib.c | 21 ++++++--
migration/multifd-zstd.c | 20 +++++--
migration/multifd.c | 90 +++++++++++++++++++++++++++-----
migration/ram.c | 1 -
migration/meson.build | 1 +
migration/trace-events | 8 +--
10 files changed, 228 insertions(+), 32 deletions(-)
create mode 100644 migration/multifd-zero-page.c
diff --git a/qapi/migration.json b/qapi/migration.json
index 83fdef73b9..2684e4e9ac 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -677,10 +677,15 @@
#
# @legacy: Perform zero page checking in main migration thread.
#
+# @multifd: Perform zero page checking in multifd sender thread if
+# multifd migration is enabled, else in the main migration
+# thread as for @legacy.
+#
# Since: 9.0
+#
##
{ 'enum': 'ZeroPageDetection',
- 'data': [ 'none', 'legacy' ] }
+ 'data': [ 'none', 'legacy', 'multifd' ] }
##
# @BitmapMigrationBitmapAliasTransform:
diff --git a/migration/multifd.h b/migration/multifd.h
index 7447c2bea3..c9d9b09239 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -55,14 +55,24 @@ typedef struct {
/* size of the next packet that contains pages */
uint32_t next_packet_size;
uint64_t packet_num;
- uint64_t unused[4]; /* Reserved for future use */
+ /* zero pages */
+ uint32_t zero_pages;
+ uint32_t unused32[1]; /* Reserved for future use */
+ uint64_t unused64[3]; /* Reserved for future use */
char ramblock[256];
+ /*
+ * This array contains the pointers to:
+ * - normal pages (initial normal_pages entries)
+ * - zero pages (following zero_pages entries)
+ */
uint64_t offset[];
} __attribute__((packed)) MultiFDPacket_t;
typedef struct {
/* number of used pages */
uint32_t num;
+ /* number of normal pages */
+ uint32_t normal_num;
/* number of allocated pages */
uint32_t allocated;
/* offset of each page */
@@ -136,6 +146,8 @@ typedef struct {
uint64_t packets_sent;
/* non zero pages sent through this channel */
uint64_t total_normal_pages;
+ /* zero pages sent through this channel */
+ uint64_t total_zero_pages;
/* buffers to send */
struct iovec *iov;
/* number of iovs used */
@@ -194,12 +206,18 @@ typedef struct {
uint8_t *host;
/* non zero pages recv through this channel */
uint64_t total_normal_pages;
+ /* zero pages recv through this channel */
+ uint64_t total_zero_pages;
/* buffers to recv */
struct iovec *iov;
/* Pages that are not zero */
ram_addr_t *normal;
/* num of non zero pages */
uint32_t normal_num;
+ /* Pages that are zero */
+ ram_addr_t *zero;
+ /* num of zero pages */
+ uint32_t zero_num;
/* used for de-compression methods */
void *compress_data;
} MultiFDRecvParams;
@@ -221,6 +239,9 @@ typedef struct {
void multifd_register_ops(int method, MultiFDMethods *ops);
void multifd_send_fill_packet(MultiFDSendParams *p);
+bool multifd_send_prepare_common(MultiFDSendParams *p);
+void multifd_send_zero_page_detect(MultiFDSendParams *p);
+void multifd_recv_zero_page_process(MultiFDRecvParams *p);
static inline void multifd_send_prepare_header(MultiFDSendParams *p)
{
diff --git a/hw/core/qdev-properties-system.c b/hw/core/qdev-properties-system.c
index 71a21bf24e..7eca2f2377 100644
--- a/hw/core/qdev-properties-system.c
+++ b/hw/core/qdev-properties-system.c
@@ -696,7 +696,7 @@ const PropertyInfo qdev_prop_granule_mode = {
const PropertyInfo qdev_prop_zero_page_detection = {
.name = "ZeroPageDetection",
.description = "zero_page_detection values, "
- "none,legacy",
+ "none,legacy,multifd",
.enum_table = &ZeroPageDetection_lookup,
.get = qdev_propinfo_get_enum,
.set = qdev_propinfo_set_enum,
diff --git a/migration/multifd-zero-page.c b/migration/multifd-zero-page.c
new file mode 100644
index 0000000000..1ba38be636
--- /dev/null
+++ b/migration/multifd-zero-page.c
@@ -0,0 +1,87 @@
+/*
+ * Multifd zero page detection implementation.
+ *
+ * Copyright (c) 2024 Bytedance Inc
+ *
+ * Authors:
+ * Hao Xiang <hao.xiang@bytedance.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/cutils.h"
+#include "exec/ramblock.h"
+#include "migration.h"
+#include "multifd.h"
+#include "options.h"
+#include "ram.h"
+
+static bool multifd_zero_page_enabled(void)
+{
+ return migrate_zero_page_detection() == ZERO_PAGE_DETECTION_MULTIFD;
+}
+
+static void swap_page_offset(ram_addr_t *pages_offset, int a, int b)
+{
+ ram_addr_t temp;
+
+ if (a == b) {
+ return;
+ }
+
+ temp = pages_offset[a];
+ pages_offset[a] = pages_offset[b];
+ pages_offset[b] = temp;
+}
+
+/**
+ * multifd_send_zero_page_detect: Perform zero page detection on all pages.
+ *
+ * Sorts normal pages before zero pages in p->pages->offset and updates
+ * p->pages->normal_num.
+ *
+ * @param p A pointer to the send params.
+ */
+void multifd_send_zero_page_detect(MultiFDSendParams *p)
+{
+ MultiFDPages_t *pages = p->pages;
+ RAMBlock *rb = pages->block;
+ int i = 0;
+ int j = pages->num - 1;
+
+ if (!multifd_zero_page_enabled()) {
+ pages->normal_num = pages->num;
+ return;
+ }
+
+ /*
+ * Sort the page offset array by moving all normal pages to
+ * the left and all zero pages to the right of the array.
+ */
+ while (i <= j) {
+ uint64_t offset = pages->offset[i];
+
+ if (!buffer_is_zero(rb->host + offset, p->page_size)) {
+ i++;
+ continue;
+ }
+
+ swap_page_offset(pages->offset, i, j);
+ ram_release_page(rb->idstr, offset);
+ j--;
+ }
+
+ pages->normal_num = i;
+}
+
+void multifd_recv_zero_page_process(MultiFDRecvParams *p)
+{
+ for (int i = 0; i < p->zero_num; i++) {
+ void *page = p->host + p->zero[i];
+ if (!buffer_is_zero(page, p->page_size)) {
+ memset(page, 0, p->page_size);
+ }
+ }
+}
diff --git a/migration/multifd-zlib.c b/migration/multifd-zlib.c
index 6120faad65..83c0374380 100644
--- a/migration/multifd-zlib.c
+++ b/migration/multifd-zlib.c
@@ -123,13 +123,15 @@ static int zlib_send_prepare(MultiFDSendParams *p, Error **errp)
int ret;
uint32_t i;
- multifd_send_prepare_header(p);
+ if (!multifd_send_prepare_common(p)) {
+ goto out;
+ }
- for (i = 0; i < pages->num; i++) {
+ for (i = 0; i < pages->normal_num; i++) {
uint32_t available = z->zbuff_len - out_size;
int flush = Z_NO_FLUSH;
- if (i == pages->num - 1) {
+ if (i == pages->normal_num - 1) {
flush = Z_SYNC_FLUSH;
}
@@ -172,10 +174,10 @@ static int zlib_send_prepare(MultiFDSendParams *p, Error **errp)
p->iov[p->iovs_num].iov_len = out_size;
p->iovs_num++;
p->next_packet_size = out_size;
- p->flags |= MULTIFD_FLAG_ZLIB;
+out:
+ p->flags |= MULTIFD_FLAG_ZLIB;
multifd_send_fill_packet(p);
-
return 0;
}
@@ -261,6 +263,14 @@ static int zlib_recv(MultiFDRecvParams *p, Error **errp)
p->id, flags, MULTIFD_FLAG_ZLIB);
return -1;
}
+
+ multifd_recv_zero_page_process(p);
+
+ if (!p->normal_num) {
+ assert(in_size == 0);
+ return 0;
+ }
+
ret = qio_channel_read_all(p->c, (void *)z->zbuff, in_size, errp);
if (ret != 0) {
@@ -310,6 +320,7 @@ static int zlib_recv(MultiFDRecvParams *p, Error **errp)
p->id, out_size, expected_size);
return -1;
}
+
return 0;
}
diff --git a/migration/multifd-zstd.c b/migration/multifd-zstd.c
index cac236833d..02112255ad 100644
--- a/migration/multifd-zstd.c
+++ b/migration/multifd-zstd.c
@@ -118,16 +118,18 @@ static int zstd_send_prepare(MultiFDSendParams *p, Error **errp)
int ret;
uint32_t i;
- multifd_send_prepare_header(p);
+ if (!multifd_send_prepare_common(p)) {
+ goto out;
+ }
z->out.dst = z->zbuff;
z->out.size = z->zbuff_len;
z->out.pos = 0;
- for (i = 0; i < pages->num; i++) {
+ for (i = 0; i < pages->normal_num; i++) {
ZSTD_EndDirective flush = ZSTD_e_continue;
- if (i == pages->num - 1) {
+ if (i == pages->normal_num - 1) {
flush = ZSTD_e_flush;
}
z->in.src = p->pages->block->host + pages->offset[i];
@@ -161,10 +163,10 @@ static int zstd_send_prepare(MultiFDSendParams *p, Error **errp)
p->iov[p->iovs_num].iov_len = z->out.pos;
p->iovs_num++;
p->next_packet_size = z->out.pos;
- p->flags |= MULTIFD_FLAG_ZSTD;
+out:
+ p->flags |= MULTIFD_FLAG_ZSTD;
multifd_send_fill_packet(p);
-
return 0;
}
@@ -257,6 +259,14 @@ static int zstd_recv(MultiFDRecvParams *p, Error **errp)
p->id, flags, MULTIFD_FLAG_ZSTD);
return -1;
}
+
+ multifd_recv_zero_page_process(p);
+
+ if (!p->normal_num) {
+ assert(in_size == 0);
+ return 0;
+ }
+
ret = qio_channel_read_all(p->c, (void *)z->zbuff, in_size, errp);
if (ret != 0) {
diff --git a/migration/multifd.c b/migration/multifd.c
index 3ba922694e..0179422f6d 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -11,6 +11,7 @@
*/
#include "qemu/osdep.h"
+#include "qemu/cutils.h"
#include "qemu/rcu.h"
#include "exec/target_page.h"
#include "sysemu/sysemu.h"
@@ -111,12 +112,17 @@ void multifd_send_channel_created(void)
static void multifd_set_file_bitmap(MultiFDSendParams *p)
{
MultiFDPages_t *pages = p->pages;
+ uint32_t zero_num = p->pages->num - p->pages->normal_num;
assert(pages->block);
- for (int i = 0; i < p->pages->num; i++) {
+ for (int i = 0; i < p->pages->normal_num; i++) {
ramblock_set_file_bmap_atomic(pages->block, pages->offset[i], true);
}
+
+ for (int i = p->pages->num; i < zero_num; i++) {
+ ramblock_set_file_bmap_atomic(pages->block, pages->offset[i], false);
+ }
}
/* Multifd without compression */
@@ -153,13 +159,13 @@ static void multifd_send_prepare_iovs(MultiFDSendParams *p)
{
MultiFDPages_t *pages = p->pages;
- for (int i = 0; i < pages->num; i++) {
+ for (int i = 0; i < pages->normal_num; i++) {
p->iov[p->iovs_num].iov_base = pages->block->host + pages->offset[i];
p->iov[p->iovs_num].iov_len = p->page_size;
p->iovs_num++;
}
- p->next_packet_size = pages->num * p->page_size;
+ p->next_packet_size = pages->normal_num * p->page_size;
}
/**
@@ -178,6 +184,8 @@ static int nocomp_send_prepare(MultiFDSendParams *p, Error **errp)
bool use_zero_copy_send = migrate_zero_copy_send();
int ret;
+ multifd_send_zero_page_detect(p);
+
if (!multifd_use_packets()) {
multifd_send_prepare_iovs(p);
multifd_set_file_bitmap(p);
@@ -261,6 +269,13 @@ static int nocomp_recv(MultiFDRecvParams *p, Error **errp)
p->id, flags, MULTIFD_FLAG_NOCOMP);
return -1;
}
+
+ multifd_recv_zero_page_process(p);
+
+ if (!p->normal_num) {
+ return 0;
+ }
+
for (int i = 0; i < p->normal_num; i++) {
p->iov[i].iov_base = p->host + p->normal[i];
p->iov[i].iov_len = p->page_size;
@@ -295,6 +310,7 @@ static void multifd_pages_reset(MultiFDPages_t *pages)
* overwritten later when reused.
*/
pages->num = 0;
+ pages->normal_num = 0;
pages->block = NULL;
}
@@ -386,11 +402,13 @@ void multifd_send_fill_packet(MultiFDSendParams *p)
MultiFDPacket_t *packet = p->packet;
MultiFDPages_t *pages = p->pages;
uint64_t packet_num;
+ uint32_t zero_num = pages->num - pages->normal_num;
int i;
packet->flags = cpu_to_be32(p->flags);
packet->pages_alloc = cpu_to_be32(p->pages->allocated);
- packet->normal_pages = cpu_to_be32(pages->num);
+ packet->normal_pages = cpu_to_be32(pages->normal_num);
+ packet->zero_pages = cpu_to_be32(zero_num);
packet->next_packet_size = cpu_to_be32(p->next_packet_size);
packet_num = qatomic_fetch_inc(&multifd_send_state->packet_num);
@@ -408,10 +426,11 @@ void multifd_send_fill_packet(MultiFDSendParams *p)
}
p->packets_sent++;
- p->total_normal_pages += pages->num;
+ p->total_normal_pages += pages->normal_num;
+ p->total_zero_pages += zero_num;
- trace_multifd_send(p->id, packet_num, pages->num, p->flags,
- p->next_packet_size);
+ trace_multifd_send(p->id, packet_num, pages->normal_num, zero_num,
+ p->flags, p->next_packet_size);
}
static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
@@ -452,20 +471,29 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
p->normal_num = be32_to_cpu(packet->normal_pages);
if (p->normal_num > packet->pages_alloc) {
error_setg(errp, "multifd: received packet "
- "with %u pages and expected maximum pages are %u",
+ "with %u normal pages and expected maximum pages are %u",
p->normal_num, packet->pages_alloc) ;
return -1;
}
+ p->zero_num = be32_to_cpu(packet->zero_pages);
+ if (p->zero_num > packet->pages_alloc - p->normal_num) {
+ error_setg(errp, "multifd: received packet "
+ "with %u zero pages and expected maximum zero pages are %u",
+ p->zero_num, packet->pages_alloc - p->normal_num) ;
+ return -1;
+ }
+
p->next_packet_size = be32_to_cpu(packet->next_packet_size);
p->packet_num = be64_to_cpu(packet->packet_num);
p->packets_recved++;
p->total_normal_pages += p->normal_num;
+ p->total_zero_pages += p->zero_num;
- trace_multifd_recv(p->id, p->packet_num, p->normal_num, p->flags,
- p->next_packet_size);
+ trace_multifd_recv(p->id, p->packet_num, p->normal_num, p->zero_num,
+ p->flags, p->next_packet_size);
- if (p->normal_num == 0) {
+ if (p->normal_num == 0 && p->zero_num == 0) {
return 0;
}
@@ -491,6 +519,18 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
p->normal[i] = offset;
}
+ for (i = 0; i < p->zero_num; i++) {
+ uint64_t offset = be64_to_cpu(packet->offset[p->normal_num + i]);
+
+ if (offset > (p->block->used_length - p->page_size)) {
+ error_setg(errp, "multifd: offset too long %" PRIu64
+ " (max " RAM_ADDR_FMT ")",
+ offset, p->block->used_length);
+ return -1;
+ }
+ p->zero[i] = offset;
+ }
+
return 0;
}
@@ -918,6 +958,8 @@ static void *multifd_send_thread(void *opaque)
stat64_add(&mig_stats.multifd_bytes,
p->next_packet_size + p->packet_len);
+ stat64_add(&mig_stats.normal_pages, pages->normal_num);
+ stat64_add(&mig_stats.zero_pages, pages->num - pages->normal_num);
multifd_pages_reset(p->pages);
p->next_packet_size = 0;
@@ -965,7 +1007,8 @@ out:
rcu_unregister_thread();
migration_threads_remove(thread);
- trace_multifd_send_thread_end(p->id, p->packets_sent, p->total_normal_pages);
+ trace_multifd_send_thread_end(p->id, p->packets_sent, p->total_normal_pages,
+ p->total_zero_pages);
return NULL;
}
@@ -1316,6 +1359,8 @@ static void multifd_recv_cleanup_channel(MultiFDRecvParams *p)
p->iov = NULL;
g_free(p->normal);
p->normal = NULL;
+ g_free(p->zero);
+ p->zero = NULL;
multifd_recv_state->ops->recv_cleanup(p);
}
@@ -1449,7 +1494,7 @@ static void *multifd_recv_thread(void *opaque)
flags = p->flags;
/* recv methods don't know how to handle the SYNC flag */
p->flags &= ~MULTIFD_FLAG_SYNC;
- has_data = !!p->normal_num;
+ has_data = p->normal_num || p->zero_num;
qemu_mutex_unlock(&p->mutex);
} else {
/*
@@ -1507,7 +1552,9 @@ static void *multifd_recv_thread(void *opaque)
}
rcu_unregister_thread();
- trace_multifd_recv_thread_end(p->id, p->packets_recved, p->total_normal_pages);
+ trace_multifd_recv_thread_end(p->id, p->packets_recved,
+ p->total_normal_pages,
+ p->total_zero_pages);
return NULL;
}
@@ -1559,6 +1606,7 @@ int multifd_recv_setup(Error **errp)
p->name = g_strdup_printf("multifdrecv_%d", i);
p->iov = g_new0(struct iovec, page_count);
p->normal = g_new0(ram_addr_t, page_count);
+ p->zero = g_new0(ram_addr_t, page_count);
p->page_count = page_count;
p->page_size = qemu_target_page_size();
}
@@ -1633,3 +1681,17 @@ void multifd_recv_new_channel(QIOChannel *ioc, Error **errp)
QEMU_THREAD_JOINABLE);
qatomic_inc(&multifd_recv_state->count);
}
+
+bool multifd_send_prepare_common(MultiFDSendParams *p)
+{
+ multifd_send_zero_page_detect(p);
+
+ if (!p->pages->normal_num) {
+ p->next_packet_size = 0;
+ return false;
+ }
+
+ multifd_send_prepare_header(p);
+
+ return true;
+}
diff --git a/migration/ram.c b/migration/ram.c
index 260529f264..c26435adc7 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1288,7 +1288,6 @@ static int ram_save_multifd_page(RAMBlock *block, ram_addr_t offset)
if (!multifd_queue_page(block, offset)) {
return -1;
}
- stat64_add(&mig_stats.normal_pages, 1);
return 1;
}
diff --git a/migration/meson.build b/migration/meson.build
index 92b1cc4297..1eeb915ff6 100644
--- a/migration/meson.build
+++ b/migration/meson.build
@@ -22,6 +22,7 @@ system_ss.add(files(
'migration.c',
'multifd.c',
'multifd-zlib.c',
+ 'multifd-zero-page.c',
'ram-compress.c',
'options.c',
'postcopy-ram.c',
diff --git a/migration/trace-events b/migration/trace-events
index bf1a069632..f0e1cb80c7 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -128,21 +128,21 @@ postcopy_preempt_reset_channel(void) ""
# multifd.c
multifd_new_send_channel_async(uint8_t id) "channel %u"
multifd_new_send_channel_async_error(uint8_t id, void *err) "channel=%u err=%p"
-multifd_recv(uint8_t id, uint64_t packet_num, uint32_t used, uint32_t flags, uint32_t next_packet_size) "channel %u packet_num %" PRIu64 " pages %u flags 0x%x next packet size %u"
+multifd_recv(uint8_t id, uint64_t packet_num, uint32_t normal, uint32_t zero, uint32_t flags, uint32_t next_packet_size) "channel %u packet_num %" PRIu64 " normal pages %u zero pages %u flags 0x%x next packet size %u"
multifd_recv_new_channel(uint8_t id) "channel %u"
multifd_recv_sync_main(long packet_num) "packet num %ld"
multifd_recv_sync_main_signal(uint8_t id) "channel %u"
multifd_recv_sync_main_wait(uint8_t id) "iter %u"
multifd_recv_terminate_threads(bool error) "error %d"
-multifd_recv_thread_end(uint8_t id, uint64_t packets, uint64_t pages) "channel %u packets %" PRIu64 " pages %" PRIu64
+multifd_recv_thread_end(uint8_t id, uint64_t packets, uint64_t normal_pages, uint64_t zero_pages) "channel %u packets %" PRIu64 " normal pages %" PRIu64 " zero pages %" PRIu64
multifd_recv_thread_start(uint8_t id) "%u"
-multifd_send(uint8_t id, uint64_t packet_num, uint32_t normal, uint32_t flags, uint32_t next_packet_size) "channel %u packet_num %" PRIu64 " normal pages %u flags 0x%x next packet size %u"
+multifd_send(uint8_t id, uint64_t packet_num, uint32_t normal_pages, uint32_t zero_pages, uint32_t flags, uint32_t next_packet_size) "channel %u packet_num %" PRIu64 " normal pages %u zero pages %u flags 0x%x next packet size %u"
multifd_send_error(uint8_t id) "channel %u"
multifd_send_sync_main(long packet_num) "packet num %ld"
multifd_send_sync_main_signal(uint8_t id) "channel %u"
multifd_send_sync_main_wait(uint8_t id) "channel %u"
multifd_send_terminate_threads(void) ""
-multifd_send_thread_end(uint8_t id, uint64_t packets, uint64_t normal_pages) "channel %u packets %" PRIu64 " normal pages %" PRIu64
+multifd_send_thread_end(uint8_t id, uint64_t packets, uint64_t normal_pages, uint64_t zero_pages) "channel %u packets %" PRIu64 " normal pages %" PRIu64 " zero pages %" PRIu64
multifd_send_thread_start(uint8_t id) "%u"
multifd_tls_outgoing_handshake_start(void *ioc, void *tioc, const char *hostname) "ioc=%p tioc=%p hostname=%s"
multifd_tls_outgoing_handshake_error(void *ioc, const char *err) "ioc=%p err=%s"
--
2.44.0