Use sendmsg() and MSG_SPLICE_PAGES rather than sendpage in ceph when
transmitting data. For the moment, this can only transmit one page at a
time because of the architecture of net/ceph/, but if
write_partial_message_data() can be given a bvec[] at a time by the
iteration code, this would allow pages to be sent in a batch.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Ilya Dryomov <idryomov@gmail.com>
cc: Xiubo Li <xiubli@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
cc: ceph-devel@vger.kernel.org
cc: netdev@vger.kernel.org
---
Notes:
ver #5)
- Switch condition for setting MSG_MORE in write_partial_message_data()
net/ceph/messenger_v1.c | 60 ++++++++++++++---------------------------
1 file changed, 20 insertions(+), 40 deletions(-)
diff --git a/net/ceph/messenger_v1.c b/net/ceph/messenger_v1.c
index d664cb1593a7..814579f27f04 100644
--- a/net/ceph/messenger_v1.c
+++ b/net/ceph/messenger_v1.c
@@ -74,37 +74,6 @@ static int ceph_tcp_sendmsg(struct socket *sock, struct kvec *iov,
return r;
}
-/*
- * @more: either or both of MSG_MORE and MSG_SENDPAGE_NOTLAST
- */
-static int ceph_tcp_sendpage(struct socket *sock, struct page *page,
- int offset, size_t size, int more)
-{
- ssize_t (*sendpage)(struct socket *sock, struct page *page,
- int offset, size_t size, int flags);
- int flags = MSG_DONTWAIT | MSG_NOSIGNAL | more;
- int ret;
-
- /*
- * sendpage cannot properly handle pages with page_count == 0,
- * we need to fall back to sendmsg if that's the case.
- *
- * Same goes for slab pages: skb_can_coalesce() allows
- * coalescing neighboring slab objects into a single frag which
- * triggers one of hardened usercopy checks.
- */
- if (sendpage_ok(page))
- sendpage = sock->ops->sendpage;
- else
- sendpage = sock_no_sendpage;
-
- ret = sendpage(sock, page, offset, size, flags);
- if (ret == -EAGAIN)
- ret = 0;
-
- return ret;
-}
-
static void con_out_kvec_reset(struct ceph_connection *con)
{
BUG_ON(con->v1.out_skip);
@@ -464,7 +433,6 @@ static int write_partial_message_data(struct ceph_connection *con)
struct ceph_msg *msg = con->out_msg;
struct ceph_msg_data_cursor *cursor = &msg->cursor;
bool do_datacrc = !ceph_test_opt(from_msgr(con->msgr), NOCRC);
- int more = MSG_MORE | MSG_SENDPAGE_NOTLAST;
u32 crc;
dout("%s %p msg %p\n", __func__, con, msg);
@@ -482,6 +450,10 @@ static int write_partial_message_data(struct ceph_connection *con)
*/
crc = do_datacrc ? le32_to_cpu(msg->footer.data_crc) : 0;
while (cursor->total_resid) {
+ struct bio_vec bvec;
+ struct msghdr msghdr = {
+ .msg_flags = MSG_SPLICE_PAGES,
+ };
struct page *page;
size_t page_offset;
size_t length;
@@ -493,10 +465,13 @@ static int write_partial_message_data(struct ceph_connection *con)
}
page = ceph_msg_data_next(cursor, &page_offset, &length);
- if (length == cursor->total_resid)
- more = MSG_MORE;
- ret = ceph_tcp_sendpage(con->sock, page, page_offset, length,
- more);
+ if (length != cursor->total_resid)
+ msghdr.msg_flags |= MSG_MORE;
+
+ bvec_set_page(&bvec, page, length, page_offset);
+ iov_iter_bvec(&msghdr.msg_iter, ITER_SOURCE, &bvec, 1, length);
+
+ ret = sock_sendmsg(con->sock, &msghdr);
if (ret <= 0) {
if (do_datacrc)
msg->footer.data_crc = cpu_to_le32(crc);
@@ -526,7 +501,10 @@ static int write_partial_message_data(struct ceph_connection *con)
*/
static int write_partial_skip(struct ceph_connection *con)
{
- int more = MSG_MORE | MSG_SENDPAGE_NOTLAST;
+ struct bio_vec bvec;
+ struct msghdr msghdr = {
+ .msg_flags = MSG_SPLICE_PAGES | MSG_MORE,
+ };
int ret;
dout("%s %p %d left\n", __func__, con, con->v1.out_skip);
@@ -534,9 +512,11 @@ static int write_partial_skip(struct ceph_connection *con)
size_t size = min(con->v1.out_skip, (int)PAGE_SIZE);
if (size == con->v1.out_skip)
- more = MSG_MORE;
- ret = ceph_tcp_sendpage(con->sock, ceph_zero_page, 0, size,
- more);
+ msghdr.msg_flags &= ~MSG_MORE;
+ bvec_set_page(&bvec, ZERO_PAGE(0), size, 0);
+ iov_iter_bvec(&msghdr.msg_iter, ITER_SOURCE, &bvec, 1, size);
+
+ ret = sock_sendmsg(con->sock, &msghdr);
if (ret <= 0)
goto out;
con->v1.out_skip -= ret;On Sat, Jun 24, 2023 at 12:55 AM David Howells <dhowells@redhat.com> wrote:
>
> Use sendmsg() and MSG_SPLICE_PAGES rather than sendpage in ceph when
> transmitting data. For the moment, this can only transmit one page at a
> time because of the architecture of net/ceph/, but if
> write_partial_message_data() can be given a bvec[] at a time by the
> iteration code, this would allow pages to be sent in a batch.
>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Ilya Dryomov <idryomov@gmail.com>
> cc: Xiubo Li <xiubli@redhat.com>
> cc: Jeff Layton <jlayton@kernel.org>
> cc: "David S. Miller" <davem@davemloft.net>
> cc: Eric Dumazet <edumazet@google.com>
> cc: Jakub Kicinski <kuba@kernel.org>
> cc: Paolo Abeni <pabeni@redhat.com>
> cc: Jens Axboe <axboe@kernel.dk>
> cc: Matthew Wilcox <willy@infradead.org>
> cc: ceph-devel@vger.kernel.org
> cc: netdev@vger.kernel.org
> ---
>
> Notes:
> ver #5)
> - Switch condition for setting MSG_MORE in write_partial_message_data()
>
> net/ceph/messenger_v1.c | 60 ++++++++++++++---------------------------
> 1 file changed, 20 insertions(+), 40 deletions(-)
>
> diff --git a/net/ceph/messenger_v1.c b/net/ceph/messenger_v1.c
> index d664cb1593a7..814579f27f04 100644
> --- a/net/ceph/messenger_v1.c
> +++ b/net/ceph/messenger_v1.c
> @@ -74,37 +74,6 @@ static int ceph_tcp_sendmsg(struct socket *sock, struct kvec *iov,
> return r;
> }
>
> -/*
> - * @more: either or both of MSG_MORE and MSG_SENDPAGE_NOTLAST
> - */
> -static int ceph_tcp_sendpage(struct socket *sock, struct page *page,
> - int offset, size_t size, int more)
> -{
> - ssize_t (*sendpage)(struct socket *sock, struct page *page,
> - int offset, size_t size, int flags);
> - int flags = MSG_DONTWAIT | MSG_NOSIGNAL | more;
> - int ret;
> -
> - /*
> - * sendpage cannot properly handle pages with page_count == 0,
> - * we need to fall back to sendmsg if that's the case.
> - *
> - * Same goes for slab pages: skb_can_coalesce() allows
> - * coalescing neighboring slab objects into a single frag which
> - * triggers one of hardened usercopy checks.
> - */
> - if (sendpage_ok(page))
> - sendpage = sock->ops->sendpage;
> - else
> - sendpage = sock_no_sendpage;
> -
> - ret = sendpage(sock, page, offset, size, flags);
> - if (ret == -EAGAIN)
> - ret = 0;
> -
> - return ret;
> -}
> -
> static void con_out_kvec_reset(struct ceph_connection *con)
> {
> BUG_ON(con->v1.out_skip);
> @@ -464,7 +433,6 @@ static int write_partial_message_data(struct ceph_connection *con)
> struct ceph_msg *msg = con->out_msg;
> struct ceph_msg_data_cursor *cursor = &msg->cursor;
> bool do_datacrc = !ceph_test_opt(from_msgr(con->msgr), NOCRC);
> - int more = MSG_MORE | MSG_SENDPAGE_NOTLAST;
> u32 crc;
>
> dout("%s %p msg %p\n", __func__, con, msg);
> @@ -482,6 +450,10 @@ static int write_partial_message_data(struct ceph_connection *con)
> */
> crc = do_datacrc ? le32_to_cpu(msg->footer.data_crc) : 0;
> while (cursor->total_resid) {
> + struct bio_vec bvec;
> + struct msghdr msghdr = {
> + .msg_flags = MSG_SPLICE_PAGES,
Hi David,
This appears to be losing MSG_DONTWAIT | MSG_NOSIGNAL flags which were
set previously?
> + };
> struct page *page;
> size_t page_offset;
> size_t length;
> @@ -493,10 +465,13 @@ static int write_partial_message_data(struct ceph_connection *con)
> }
>
> page = ceph_msg_data_next(cursor, &page_offset, &length);
> - if (length == cursor->total_resid)
> - more = MSG_MORE;
> - ret = ceph_tcp_sendpage(con->sock, page, page_offset, length,
> - more);
> + if (length != cursor->total_resid)
> + msghdr.msg_flags |= MSG_MORE;
> +
> + bvec_set_page(&bvec, page, length, page_offset);
> + iov_iter_bvec(&msghdr.msg_iter, ITER_SOURCE, &bvec, 1, length);
> +
> + ret = sock_sendmsg(con->sock, &msghdr);
> if (ret <= 0) {
And this is losing munging -EAGAIN -> 0?
> if (do_datacrc)
> msg->footer.data_crc = cpu_to_le32(crc);
> @@ -526,7 +501,10 @@ static int write_partial_message_data(struct ceph_connection *con)
> */
> static int write_partial_skip(struct ceph_connection *con)
> {
> - int more = MSG_MORE | MSG_SENDPAGE_NOTLAST;
> + struct bio_vec bvec;
> + struct msghdr msghdr = {
> + .msg_flags = MSG_SPLICE_PAGES | MSG_MORE,
> + };
> int ret;
>
> dout("%s %p %d left\n", __func__, con, con->v1.out_skip);
> @@ -534,9 +512,11 @@ static int write_partial_skip(struct ceph_connection *con)
> size_t size = min(con->v1.out_skip, (int)PAGE_SIZE);
>
> if (size == con->v1.out_skip)
> - more = MSG_MORE;
> - ret = ceph_tcp_sendpage(con->sock, ceph_zero_page, 0, size,
> - more);
> + msghdr.msg_flags &= ~MSG_MORE;
> + bvec_set_page(&bvec, ZERO_PAGE(0), size, 0);
> + iov_iter_bvec(&msghdr.msg_iter, ITER_SOURCE, &bvec, 1, size);
> +
> + ret = sock_sendmsg(con->sock, &msghdr);
> if (ret <= 0)
Same here... I would suggest that you keep ceph_tcp_sendpage() function
and make only minimal modifications to avoid regressions.
Thanks,
Ilya
Ilya Dryomov <idryomov@gmail.com> wrote: > > - int flags = MSG_DONTWAIT | MSG_NOSIGNAL | more; Btw, why are you setting MSG_DONTWAIT? If you're in the middle of transmitting a message on a TCP socket, surely you can't just switch to transmitting a different message on the same socket without doing some sort of reframing? David
On Mon, Jun 26, 2023 at 5:12 PM David Howells <dhowells@redhat.com> wrote:
>
> Ilya Dryomov <idryomov@gmail.com> wrote:
>
> > > - int flags = MSG_DONTWAIT | MSG_NOSIGNAL | more;
>
> Btw, why are you setting MSG_DONTWAIT? If you're in the middle of
> transmitting a message on a TCP socket, surely you can't just switch to
> transmitting a different message on the same socket without doing some sort of
> reframing?
We don't want to hog kworker threads. You are correct that we can't
switch to transmitting a different message on the same socket but Ceph
is massively parallel and there can be dozens or even hundreds of other
sockets to work on.
Thanks,
Ilya
Ilya Dryomov <idryomov@gmail.com> wrote: > Same here... I would suggest that you keep ceph_tcp_sendpage() function > and make only minimal modifications to avoid regressions. This is now committed to net-next. I can bring ceph_tcp_sendpage() back into existence or fix it in place for now if you have a preference. Note that I'm working on patches to rework the libceph transmission path so that it isn't dealing with transmitting a single page at a time, but it's not ready yet. David
On Mon, Jun 26, 2023 at 4:00 PM David Howells <dhowells@redhat.com> wrote:
>
> Ilya Dryomov <idryomov@gmail.com> wrote:
>
> > Same here... I would suggest that you keep ceph_tcp_sendpage() function
> > and make only minimal modifications to avoid regressions.
>
> This is now committed to net-next.
This needs to be dropped from linux-next because both this and
especially the other (net/ceph/messenger_v2.c) patch introduce
regressions.
> I can bring ceph_tcp_sendpage() back into
> existence or fix it in place for now if you have a preference.
I already mentioned that I would prefer if ceph_tcp_sendpage() was
brought back into existence.
>
> Note that I'm working on patches to rework the libceph transmission path so
> that it isn't dealing with transmitting a single page at a time, but it's not
> ready yet.
That is a worthwhile improvement now that sock_sendmsg() can take
advantage of multiple pages! It would be pretty invasive though so
I think ceph_tcp_sendpage() is better to remain in place until then.
Thanks,
Ilya
Ilya Dryomov <idryomov@gmail.com> wrote: > > This is now committed to net-next. > > This needs to be dropped from linux-next because both this and > especially the other (net/ceph/messenger_v2.c) patch introduce > regressions. net-next, not linux-next. I'm not sure they drop things from there rather than reverting them. David
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