When transmitting data, call down into TCP using a single sendmsg with
MSG_SPLICE_PAGES to indicate that content should be spliced rather than
performing several sendmsg and sendpage calls to transmit header, data
pages and trailer.
To make this work, the data is assembled in a bio_vec array and attached to
a BVEC-type iterator. The header and trailer are copied into page
fragments so that they can be freed with put_page and attached to iterators
of their own. An iterator-of-iterators is then created to bridge all three
iterators (headers, data, trailer) and that is passed to sendmsg to pass
the entire message in a single call.
Signed-off-by: David Howells <[email protected]>
cc: Trond Myklebust <[email protected]>
cc: Anna Schumaker <[email protected]>
cc: Chuck Lever <[email protected]>
cc: Jeff Layton <[email protected]>
cc: "David S. Miller" <[email protected]>
cc: Eric Dumazet <[email protected]>
cc: Jakub Kicinski <[email protected]>
cc: Paolo Abeni <[email protected]>
cc: Jens Axboe <[email protected]>
cc: Matthew Wilcox <[email protected]>
cc: [email protected]
cc: [email protected]
---
include/linux/sunrpc/svc.h | 11 +++--
net/sunrpc/svcsock.c | 89 +++++++++++++++-----------------------
2 files changed, 40 insertions(+), 60 deletions(-)
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 877891536c2f..456ae554aa11 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -161,16 +161,15 @@ static inline bool svc_put_not_last(struct svc_serv *serv)
extern u32 svc_max_payload(const struct svc_rqst *rqstp);
/*
- * RPC Requsts and replies are stored in one or more pages.
+ * RPC Requests and replies are stored in one or more pages.
* We maintain an array of pages for each server thread.
* Requests are copied into these pages as they arrive. Remaining
* pages are available to write the reply into.
*
- * Pages are sent using ->sendpage so each server thread needs to
- * allocate more to replace those used in sending. To help keep track
- * of these pages we have a receive list where all pages initialy live,
- * and a send list where pages are moved to when there are to be part
- * of a reply.
+ * Pages are sent using ->sendmsg with MSG_SPLICE_PAGES so each server thread
+ * needs to allocate more to replace those used in sending. To help keep track
+ * of these pages we have a receive list where all pages initialy live, and a
+ * send list where pages are moved to when there are to be part of a reply.
*
* We use xdr_buf for holding responses as it fits well with NFS
* read responses (that have a header, and some data pages, and possibly
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 03a4f5615086..f1cc53aad6e0 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1060,16 +1060,8 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
return 0; /* record not complete */
}
-static int svc_tcp_send_kvec(struct socket *sock, const struct kvec *vec,
- int flags)
-{
- return kernel_sendpage(sock, virt_to_page(vec->iov_base),
- offset_in_page(vec->iov_base),
- vec->iov_len, flags);
-}
-
/*
- * kernel_sendpage() is used exclusively to reduce the number of
+ * MSG_SPLICE_PAGES is used exclusively to reduce the number of
* copy operations in this path. Therefore the caller must ensure
* that the pages backing @xdr are unchanging.
*
@@ -1081,65 +1073,54 @@ static int svc_tcp_sendmsg(struct socket *sock, struct xdr_buf *xdr,
{
const struct kvec *head = xdr->head;
const struct kvec *tail = xdr->tail;
- struct kvec rm = {
- .iov_base = &marker,
- .iov_len = sizeof(marker),
- };
+ struct iov_iter iters[3];
+ struct bio_vec head_bv, tail_bv;
struct msghdr msg = {
- .msg_flags = 0,
+ .msg_flags = MSG_SPLICE_PAGES,
};
- int ret;
+ void *m, *t;
+ int ret, n = 2, size;
*sentp = 0;
ret = xdr_alloc_bvec(xdr, GFP_KERNEL);
if (ret < 0)
return ret;
- ret = kernel_sendmsg(sock, &msg, &rm, 1, rm.iov_len);
- if (ret < 0)
- return ret;
- *sentp += ret;
- if (ret != rm.iov_len)
- return -EAGAIN;
+ m = page_frag_alloc(NULL, sizeof(marker) + head->iov_len + tail->iov_len,
+ GFP_KERNEL);
+ if (!m)
+ return -ENOMEM;
- ret = svc_tcp_send_kvec(sock, head, 0);
- if (ret < 0)
- return ret;
- *sentp += ret;
- if (ret != head->iov_len)
- goto out;
+ memcpy(m, &marker, sizeof(marker));
+ if (head->iov_len)
+ memcpy(m + sizeof(marker), head->iov_base, head->iov_len);
+ bvec_set_virt(&head_bv, m, sizeof(marker) + head->iov_len);
+ iov_iter_bvec(&iters[0], ITER_SOURCE, &head_bv, 1,
+ sizeof(marker) + head->iov_len);
- if (xdr->page_len) {
- unsigned int offset, len, remaining;
- struct bio_vec *bvec;
-
- bvec = xdr->bvec + (xdr->page_base >> PAGE_SHIFT);
- offset = offset_in_page(xdr->page_base);
- remaining = xdr->page_len;
- while (remaining > 0) {
- len = min(remaining, bvec->bv_len - offset);
- ret = kernel_sendpage(sock, bvec->bv_page,
- bvec->bv_offset + offset,
- len, 0);
- if (ret < 0)
- return ret;
- *sentp += ret;
- if (ret != len)
- goto out;
- remaining -= len;
- offset = 0;
- bvec++;
- }
- }
+ iov_iter_bvec(&iters[1], ITER_SOURCE, xdr->bvec,
+ xdr_buf_pagecount(xdr), xdr->page_len);
if (tail->iov_len) {
- ret = svc_tcp_send_kvec(sock, tail, 0);
- if (ret < 0)
- return ret;
- *sentp += ret;
+ t = page_frag_alloc(NULL, tail->iov_len, GFP_KERNEL);
+ if (!t)
+ return -ENOMEM;
+ memcpy(t, tail->iov_base, tail->iov_len);
+ bvec_set_virt(&tail_bv, t, tail->iov_len);
+ iov_iter_bvec(&iters[2], ITER_SOURCE, &tail_bv, 1, tail->iov_len);
+ n++;
}
-out:
+ size = sizeof(marker) + head->iov_len + xdr->page_len + tail->iov_len;
+ iov_iter_iterlist(&msg.msg_iter, ITER_SOURCE, iters, n, size);
+
+ ret = sock_sendmsg(sock, &msg);
+ if (ret < 0)
+ return ret;
+ if (ret > 0)
+ *sentp = ret;
+ if (ret != size)
+ return -EAGAIN;
return 0;
}
Chuck Lever III <[email protected]> wrote:
> > + if (ret > 0)
> > + *sentp = ret;
Should that be:
*sentp = ret - sizeof(marker);
David
David Howells <[email protected]> wrote:
> Chuck Lever III <[email protected]> wrote:
>
> > Simply replacing the kernel_sendpage() loop would be a
> > straightforward change and easy to evaluate and test, and
> > I'd welcome that without hesitation.
>
> How about the attached for a first phase?
>
> It does three sendmsgs, one for the marker + header, one for the body and one
> for the tail.
... And this as a second phase.
David
---
sunrpc: Allow xdr->bvec[] to be extended to do a single sendmsg
Allow xdr->bvec[] to be extended and insert the marker, the header and the
tail into it so that a single sendmsg() can be used to transmit the message.
I wonder if it would be possible to insert the marker at the beginning of the
head buffer.
Signed-off-by: David Howells <[email protected]>
cc: Trond Myklebust <[email protected]>
cc: Anna Schumaker <[email protected]>
cc: Chuck Lever <[email protected]>
cc: Jeff Layton <[email protected]>
cc: "David S. Miller" <[email protected]>
cc: Eric Dumazet <[email protected]>
cc: Jakub Kicinski <[email protected]>
cc: Paolo Abeni <[email protected]>
cc: Jens Axboe <[email protected]>
cc: Matthew Wilcox <[email protected]>
cc: [email protected]
cc: [email protected]
---
include/linux/sunrpc/xdr.h | 2 -
net/sunrpc/svcsock.c | 46 ++++++++++++++-------------------------------
net/sunrpc/xdr.c | 19 ++++++++++--------
net/sunrpc/xprtsock.c | 6 ++---
4 files changed, 30 insertions(+), 43 deletions(-)
diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index 72014c9216fc..c74ea483228b 100644
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -137,7 +137,7 @@ void xdr_inline_pages(struct xdr_buf *, unsigned int,
struct page **, unsigned int, unsigned int);
void xdr_terminate_string(const struct xdr_buf *, const u32);
size_t xdr_buf_pagecount(const struct xdr_buf *buf);
-int xdr_alloc_bvec(struct xdr_buf *buf, gfp_t gfp);
+int xdr_alloc_bvec(struct xdr_buf *buf, gfp_t gfp, unsigned int head, unsigned int tail);
void xdr_free_bvec(struct xdr_buf *buf);
static inline __be32 *xdr_encode_array(__be32 *p, const void *s, unsigned int len)
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 14efcc08c6f8..e55761fe1ccf 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -569,7 +569,7 @@ static int svc_udp_sendto(struct svc_rqst *rqstp)
if (svc_xprt_is_dead(xprt))
goto out_notconn;
- err = xdr_alloc_bvec(xdr, GFP_KERNEL);
+ err = xdr_alloc_bvec(xdr, GFP_KERNEL, 0, 0);
if (err < 0)
goto out_unlock;
@@ -1073,45 +1073,29 @@ static int svc_tcp_sendmsg(struct socket *sock, struct xdr_buf *xdr,
{
const struct kvec *head = xdr->head;
const struct kvec *tail = xdr->tail;
- struct kvec kv[2];
- struct msghdr msg = { .msg_flags = MSG_SPLICE_PAGES | MSG_MORE, };
- size_t sent;
+ struct msghdr msg = { .msg_flags = MSG_SPLICE_PAGES, };
+ size_t n;
int ret;
*sentp = 0;
- ret = xdr_alloc_bvec(xdr, GFP_KERNEL);
+ ret = xdr_alloc_bvec(xdr, GFP_KERNEL, 2, 1);
if (ret < 0)
return ret;
- kv[0].iov_base = ▮
- kv[0].iov_len = sizeof(marker);
- kv[1] = *head;
- iov_iter_kvec(&msg.msg_iter, ITER_SOURCE, kv, 2, sizeof(marker) + head->iov_len);
+ n = 2 + xdr_buf_pagecount(xdr);
+ bvec_set_virt(&xdr->bvec[0], &marker, sizeof(marker));
+ bvec_set_virt(&xdr->bvec[1], head->iov_base, head->iov_len);
+ bvec_set_virt(&xdr->bvec[n], tail->iov_base, tail->iov_len);
+ if (tail->iov_len)
+ n++;
+ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, xdr->bvec, n,
+ sizeof(marker) + xdr->len);
ret = sock_sendmsg(sock, &msg);
if (ret < 0)
return ret;
- sent = ret;
-
- if (!tail->iov_len)
- msg.msg_flags &= ~MSG_MORE;
- iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, xdr->bvec,
- xdr_buf_pagecount(xdr), xdr->page_len);
- ret = sock_sendmsg(sock, &msg);
- if (ret < 0)
- return ret;
- sent += ret;
-
- if (tail->iov_len) {
- msg.msg_flags &= ~MSG_MORE;
- iov_iter_kvec(&msg.msg_iter, ITER_SOURCE, tail, 1, tail->iov_len);
- ret = sock_sendmsg(sock, &msg);
- if (ret < 0)
- return ret;
- sent += ret;
- }
- if (sent > 0)
- *sentp = sent;
- if (sent != sizeof(marker) + xdr->len)
+ if (ret > 0)
+ *sentp = ret;
+ if (ret != sizeof(marker) + xdr->len)
return -EAGAIN;
return 0;
}
diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 36835b2f5446..695821963849 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -141,18 +141,21 @@ size_t xdr_buf_pagecount(const struct xdr_buf *buf)
}
int
-xdr_alloc_bvec(struct xdr_buf *buf, gfp_t gfp)
+xdr_alloc_bvec(struct xdr_buf *buf, gfp_t gfp, unsigned int head, unsigned int tail)
{
- size_t i, n = xdr_buf_pagecount(buf);
+ size_t i, j = 0, n = xdr_buf_pagecount(buf);
- if (n != 0 && buf->bvec == NULL) {
- buf->bvec = kmalloc_array(n, sizeof(buf->bvec[0]), gfp);
+ if (head + n + tail != 0 && buf->bvec == NULL) {
+ buf->bvec = kmalloc_array(head + n + tail,
+ sizeof(buf->bvec[0]), gfp);
if (!buf->bvec)
return -ENOMEM;
- for (i = 0; i < n; i++) {
- bvec_set_page(&buf->bvec[i], buf->pages[i], PAGE_SIZE,
- 0);
- }
+ for (i = 0; i < head; i++)
+ bvec_set_page(&buf->bvec[j++], NULL, 0, 0);
+ for (i = 0; i < n; i++)
+ bvec_set_page(&buf->bvec[j++], buf->pages[i], PAGE_SIZE, 0);
+ for (i = 0; i < tail; i++)
+ bvec_set_page(&buf->bvec[j++], NULL, 0, 0);
}
return 0;
}
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index adcbedc244d6..fdf67e84b1c7 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -825,7 +825,7 @@ static int xs_stream_nospace(struct rpc_rqst *req, bool vm_wait)
static int xs_stream_prepare_request(struct rpc_rqst *req, struct xdr_buf *buf)
{
- return xdr_alloc_bvec(buf, rpc_task_gfp_mask());
+ return xdr_alloc_bvec(buf, rpc_task_gfp_mask(), 0, 0);
}
/*
@@ -954,7 +954,7 @@ static int xs_udp_send_request(struct rpc_rqst *req)
if (!xprt_request_get_cong(xprt, req))
return -EBADSLT;
- status = xdr_alloc_bvec(xdr, rpc_task_gfp_mask());
+ status = xdr_alloc_bvec(xdr, rpc_task_gfp_mask(), 0, 0);
if (status < 0)
return status;
req->rq_xtime = ktime_get();
@@ -2591,7 +2591,7 @@ static int bc_sendto(struct rpc_rqst *req)
int err;
req->rq_xtime = ktime_get();
- err = xdr_alloc_bvec(xdr, rpc_task_gfp_mask());
+ err = xdr_alloc_bvec(xdr, rpc_task_gfp_mask(), 0, 0);
if (err < 0)
return err;
err = xprt_sock_sendmsg(transport->sock, &msg, xdr, 0, marker, &sent);
Chuck Lever III <[email protected]> wrote:
> Don't. Just change svc_tcp_send_kvec() to use sock_sendmsg, and
> leave the marker alone for now, please.
If you insist. See attached.
David
---
sunrpc: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage
When transmitting data, call down into TCP using sendmsg with
MSG_SPLICE_PAGES to indicate that content should be spliced rather than
performing sendpage calls to transmit header, data pages and trailer.
Signed-off-by: David Howells <[email protected]>
cc: Trond Myklebust <[email protected]>
cc: Anna Schumaker <[email protected]>
cc: Chuck Lever <[email protected]>
cc: Jeff Layton <[email protected]>
cc: "David S. Miller" <[email protected]>
cc: Eric Dumazet <[email protected]>
cc: Jakub Kicinski <[email protected]>
cc: Paolo Abeni <[email protected]>
cc: Jens Axboe <[email protected]>
cc: Matthew Wilcox <[email protected]>
cc: [email protected]
cc: [email protected]
---
include/linux/sunrpc/svc.h | 11 +++++------
net/sunrpc/svcsock.c | 40 +++++++++++++---------------------------
2 files changed, 18 insertions(+), 33 deletions(-)
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 877891536c2f..456ae554aa11 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -161,16 +161,15 @@ static inline bool svc_put_not_last(struct svc_serv *serv)
extern u32 svc_max_payload(const struct svc_rqst *rqstp);
/*
- * RPC Requsts and replies are stored in one or more pages.
+ * RPC Requests and replies are stored in one or more pages.
* We maintain an array of pages for each server thread.
* Requests are copied into these pages as they arrive. Remaining
* pages are available to write the reply into.
*
- * Pages are sent using ->sendpage so each server thread needs to
- * allocate more to replace those used in sending. To help keep track
- * of these pages we have a receive list where all pages initialy live,
- * and a send list where pages are moved to when there are to be part
- * of a reply.
+ * Pages are sent using ->sendmsg with MSG_SPLICE_PAGES so each server thread
+ * needs to allocate more to replace those used in sending. To help keep track
+ * of these pages we have a receive list where all pages initialy live, and a
+ * send list where pages are moved to when there are to be part of a reply.
*
* We use xdr_buf for holding responses as it fits well with NFS
* read responses (that have a header, and some data pages, and possibly
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 03a4f5615086..af146e053dfc 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1059,17 +1059,18 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
svc_xprt_received(rqstp->rq_xprt);
return 0; /* record not complete */
}
-
+
static int svc_tcp_send_kvec(struct socket *sock, const struct kvec *vec,
int flags)
{
- return kernel_sendpage(sock, virt_to_page(vec->iov_base),
- offset_in_page(vec->iov_base),
- vec->iov_len, flags);
+ struct msghdr msg = { .msg_flags = MSG_SPLICE_PAGES | flags, };
+
+ iov_iter_kvec(&msg.msg_iter, ITER_SOURCE, vec, 1, vec->iov_len);
+ return sock_sendmsg(sock, &msg);
}
/*
- * kernel_sendpage() is used exclusively to reduce the number of
+ * MSG_SPLICE_PAGES is used exclusively to reduce the number of
* copy operations in this path. Therefore the caller must ensure
* that the pages backing @xdr are unchanging.
*
@@ -1109,28 +1110,13 @@ static int svc_tcp_sendmsg(struct socket *sock, struct xdr_buf *xdr,
if (ret != head->iov_len)
goto out;
- if (xdr->page_len) {
- unsigned int offset, len, remaining;
- struct bio_vec *bvec;
-
- bvec = xdr->bvec + (xdr->page_base >> PAGE_SHIFT);
- offset = offset_in_page(xdr->page_base);
- remaining = xdr->page_len;
- while (remaining > 0) {
- len = min(remaining, bvec->bv_len - offset);
- ret = kernel_sendpage(sock, bvec->bv_page,
- bvec->bv_offset + offset,
- len, 0);
- if (ret < 0)
- return ret;
- *sentp += ret;
- if (ret != len)
- goto out;
- remaining -= len;
- offset = 0;
- bvec++;
- }
- }
+ msg.msg_flags = MSG_SPLICE_PAGES;
+ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, xdr->bvec,
+ xdr_buf_pagecount(xdr), xdr->page_len);
+ ret = sock_sendmsg(sock, &msg);
+ if (ret < 0)
+ return ret;
+ *sentp += ret;
if (tail->iov_len) {
ret = svc_tcp_send_kvec(sock, tail, 0);
> On Mar 30, 2023, at 10:26 AM, David Howells <[email protected]> wrote:
>
> Chuck Lever III <[email protected]> wrote:
>
>> Don't. Just change svc_tcp_send_kvec() to use sock_sendmsg, and
>> leave the marker alone for now, please.
>
> If you insist. See attached.
Very good, thank you for accommodating my regression paranoia.
Acked-by: Chuck Lever <[email protected]>
>
> David
> ---
> sunrpc: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage
>
> When transmitting data, call down into TCP using sendmsg with
> MSG_SPLICE_PAGES to indicate that content should be spliced rather than
> performing sendpage calls to transmit header, data pages and trailer.
>
> Signed-off-by: David Howells <[email protected]>
> cc: Trond Myklebust <[email protected]>
> cc: Anna Schumaker <[email protected]>
> cc: Chuck Lever <[email protected]>
> cc: Jeff Layton <[email protected]>
> cc: "David S. Miller" <[email protected]>
> cc: Eric Dumazet <[email protected]>
> cc: Jakub Kicinski <[email protected]>
> cc: Paolo Abeni <[email protected]>
> cc: Jens Axboe <[email protected]>
> cc: Matthew Wilcox <[email protected]>
> cc: [email protected]
> cc: [email protected]
> ---
> include/linux/sunrpc/svc.h | 11 +++++------
> net/sunrpc/svcsock.c | 40 +++++++++++++---------------------------
> 2 files changed, 18 insertions(+), 33 deletions(-)
>
> diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
> index 877891536c2f..456ae554aa11 100644
> --- a/include/linux/sunrpc/svc.h
> +++ b/include/linux/sunrpc/svc.h
> @@ -161,16 +161,15 @@ static inline bool svc_put_not_last(struct svc_serv *serv)
> extern u32 svc_max_payload(const struct svc_rqst *rqstp);
>
> /*
> - * RPC Requsts and replies are stored in one or more pages.
> + * RPC Requests and replies are stored in one or more pages.
> * We maintain an array of pages for each server thread.
> * Requests are copied into these pages as they arrive. Remaining
> * pages are available to write the reply into.
> *
> - * Pages are sent using ->sendpage so each server thread needs to
> - * allocate more to replace those used in sending. To help keep track
> - * of these pages we have a receive list where all pages initialy live,
> - * and a send list where pages are moved to when there are to be part
> - * of a reply.
> + * Pages are sent using ->sendmsg with MSG_SPLICE_PAGES so each server thread
> + * needs to allocate more to replace those used in sending. To help keep track
> + * of these pages we have a receive list where all pages initialy live, and a
> + * send list where pages are moved to when there are to be part of a reply.
> *
> * We use xdr_buf for holding responses as it fits well with NFS
> * read responses (that have a header, and some data pages, and possibly
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index 03a4f5615086..af146e053dfc 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -1059,17 +1059,18 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
> svc_xprt_received(rqstp->rq_xprt);
> return 0; /* record not complete */
> }
> -
> +
> static int svc_tcp_send_kvec(struct socket *sock, const struct kvec *vec,
> int flags)
> {
> - return kernel_sendpage(sock, virt_to_page(vec->iov_base),
> - offset_in_page(vec->iov_base),
> - vec->iov_len, flags);
> + struct msghdr msg = { .msg_flags = MSG_SPLICE_PAGES | flags, };
> +
> + iov_iter_kvec(&msg.msg_iter, ITER_SOURCE, vec, 1, vec->iov_len);
> + return sock_sendmsg(sock, &msg);
> }
>
> /*
> - * kernel_sendpage() is used exclusively to reduce the number of
> + * MSG_SPLICE_PAGES is used exclusively to reduce the number of
> * copy operations in this path. Therefore the caller must ensure
> * that the pages backing @xdr are unchanging.
> *
> @@ -1109,28 +1110,13 @@ static int svc_tcp_sendmsg(struct socket *sock, struct xdr_buf *xdr,
> if (ret != head->iov_len)
> goto out;
>
> - if (xdr->page_len) {
> - unsigned int offset, len, remaining;
> - struct bio_vec *bvec;
> -
> - bvec = xdr->bvec + (xdr->page_base >> PAGE_SHIFT);
> - offset = offset_in_page(xdr->page_base);
> - remaining = xdr->page_len;
> - while (remaining > 0) {
> - len = min(remaining, bvec->bv_len - offset);
> - ret = kernel_sendpage(sock, bvec->bv_page,
> - bvec->bv_offset + offset,
> - len, 0);
> - if (ret < 0)
> - return ret;
> - *sentp += ret;
> - if (ret != len)
> - goto out;
> - remaining -= len;
> - offset = 0;
> - bvec++;
> - }
> - }
> + msg.msg_flags = MSG_SPLICE_PAGES;
> + iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, xdr->bvec,
> + xdr_buf_pagecount(xdr), xdr->page_len);
> + ret = sock_sendmsg(sock, &msg);
> + if (ret < 0)
> + return ret;
> + *sentp += ret;
>
> if (tail->iov_len) {
> ret = svc_tcp_send_kvec(sock, tail, 0);
>
--
Chuck Lever
I gave this a spin because I had noticed a previous regression around
the 5.7 time frame in sendpage/sendmsg code changes:
https://bugzilla.kernel.org/show_bug.cgi?id=209439
In that case there was a noticeable regression in performance for high
performance servers (100gbit).
I see no such performance problems with David's iov-sendpage branch
and it all looks good to me with simple benchmarks (100gbit server,
100 x 1gbit clients reading data).
Tested-by: Daire Byrne <[email protected]>
Cheers,
Daire
On Thu, 30 Mar 2023 at 17:37, Chuck Lever III <[email protected]> wrote:
>
>
>
> > On Mar 30, 2023, at 10:26 AM, David Howells <[email protected]> wrote:
> >
> > Chuck Lever III <[email protected]> wrote:
> >
> >> Don't. Just change svc_tcp_send_kvec() to use sock_sendmsg, and
> >> leave the marker alone for now, please.
> >
> > If you insist. See attached.
>
> Very good, thank you for accommodating my regression paranoia.
>
> Acked-by: Chuck Lever <[email protected]>
>
>
> >
> > David
> > ---
> > sunrpc: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage
> >
> > When transmitting data, call down into TCP using sendmsg with
> > MSG_SPLICE_PAGES to indicate that content should be spliced rather than
> > performing sendpage calls to transmit header, data pages and trailer.
> >
> > Signed-off-by: David Howells <[email protected]>
> > cc: Trond Myklebust <[email protected]>
> > cc: Anna Schumaker <[email protected]>
> > cc: Chuck Lever <[email protected]>
> > cc: Jeff Layton <[email protected]>
> > cc: "David S. Miller" <[email protected]>
> > cc: Eric Dumazet <[email protected]>
> > cc: Jakub Kicinski <[email protected]>
> > cc: Paolo Abeni <[email protected]>
> > cc: Jens Axboe <[email protected]>
> > cc: Matthew Wilcox <[email protected]>
> > cc: [email protected]
> > cc: [email protected]
> > ---
> > include/linux/sunrpc/svc.h | 11 +++++------
> > net/sunrpc/svcsock.c | 40 +++++++++++++---------------------------
> > 2 files changed, 18 insertions(+), 33 deletions(-)
> >
> > diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
> > index 877891536c2f..456ae554aa11 100644
> > --- a/include/linux/sunrpc/svc.h
> > +++ b/include/linux/sunrpc/svc.h
> > @@ -161,16 +161,15 @@ static inline bool svc_put_not_last(struct svc_serv *serv)
> > extern u32 svc_max_payload(const struct svc_rqst *rqstp);
> >
> > /*
> > - * RPC Requsts and replies are stored in one or more pages.
> > + * RPC Requests and replies are stored in one or more pages.
> > * We maintain an array of pages for each server thread.
> > * Requests are copied into these pages as they arrive. Remaining
> > * pages are available to write the reply into.
> > *
> > - * Pages are sent using ->sendpage so each server thread needs to
> > - * allocate more to replace those used in sending. To help keep track
> > - * of these pages we have a receive list where all pages initialy live,
> > - * and a send list where pages are moved to when there are to be part
> > - * of a reply.
> > + * Pages are sent using ->sendmsg with MSG_SPLICE_PAGES so each server thread
> > + * needs to allocate more to replace those used in sending. To help keep track
> > + * of these pages we have a receive list where all pages initialy live, and a
> > + * send list where pages are moved to when there are to be part of a reply.
> > *
> > * We use xdr_buf for holding responses as it fits well with NFS
> > * read responses (that have a header, and some data pages, and possibly
> > diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> > index 03a4f5615086..af146e053dfc 100644
> > --- a/net/sunrpc/svcsock.c
> > +++ b/net/sunrpc/svcsock.c
> > @@ -1059,17 +1059,18 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp)
> > svc_xprt_received(rqstp->rq_xprt);
> > return 0; /* record not complete */
> > }
> > -
> > +
> > static int svc_tcp_send_kvec(struct socket *sock, const struct kvec *vec,
> > int flags)
> > {
> > - return kernel_sendpage(sock, virt_to_page(vec->iov_base),
> > - offset_in_page(vec->iov_base),
> > - vec->iov_len, flags);
> > + struct msghdr msg = { .msg_flags = MSG_SPLICE_PAGES | flags, };
> > +
> > + iov_iter_kvec(&msg.msg_iter, ITER_SOURCE, vec, 1, vec->iov_len);
> > + return sock_sendmsg(sock, &msg);
> > }
> >
> > /*
> > - * kernel_sendpage() is used exclusively to reduce the number of
> > + * MSG_SPLICE_PAGES is used exclusively to reduce the number of
> > * copy operations in this path. Therefore the caller must ensure
> > * that the pages backing @xdr are unchanging.
> > *
> > @@ -1109,28 +1110,13 @@ static int svc_tcp_sendmsg(struct socket *sock, struct xdr_buf *xdr,
> > if (ret != head->iov_len)
> > goto out;
> >
> > - if (xdr->page_len) {
> > - unsigned int offset, len, remaining;
> > - struct bio_vec *bvec;
> > -
> > - bvec = xdr->bvec + (xdr->page_base >> PAGE_SHIFT);
> > - offset = offset_in_page(xdr->page_base);
> > - remaining = xdr->page_len;
> > - while (remaining > 0) {
> > - len = min(remaining, bvec->bv_len - offset);
> > - ret = kernel_sendpage(sock, bvec->bv_page,
> > - bvec->bv_offset + offset,
> > - len, 0);
> > - if (ret < 0)
> > - return ret;
> > - *sentp += ret;
> > - if (ret != len)
> > - goto out;
> > - remaining -= len;
> > - offset = 0;
> > - bvec++;
> > - }
> > - }
> > + msg.msg_flags = MSG_SPLICE_PAGES;
> > + iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, xdr->bvec,
> > + xdr_buf_pagecount(xdr), xdr->page_len);
> > + ret = sock_sendmsg(sock, &msg);
> > + if (ret < 0)
> > + return ret;
> > + *sentp += ret;
> >
> > if (tail->iov_len) {
> > ret = svc_tcp_send_kvec(sock, tail, 0);
> >
>
> --
> Chuck Lever
>
>