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Message-ID: <822317.1680186419@warthog.procyon.org.uk>
Date: Thu, 30 Mar 2023 15:26:59 +0100
From: David Howells <dhowells@...hat.com>
To: Chuck Lever III <chuck.lever@...cle.com>
Cc: dhowells@...hat.com, Matthew Wilcox <willy@...radead.org>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Al Viro <viro@...iv.linux.org.uk>,
Christoph Hellwig <hch@...radead.org>,
Jens Axboe <axboe@...nel.dk>, Jeff Layton <jlayton@...nel.org>,
Christian Brauner <brauner@...nel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
"open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux Memory Management List <linux-mm@...ck.org>,
Trond Myklebust <trond.myklebust@...merspace.com>,
Anna Schumaker <anna@...nel.org>,
Linux NFS Mailing List <linux-nfs@...r.kernel.org>
Subject: Re: [RFC PATCH v2 40/48] sunrpc: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage
Chuck Lever III <chuck.lever@...cle.com> 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 <dhowells@...hat.com>
cc: Trond Myklebust <trond.myklebust@...merspace.com>
cc: Anna Schumaker <anna@...nel.org>
cc: Chuck Lever <chuck.lever@...cle.com>
cc: Jeff Layton <jlayton@...nel.org>
cc: "David S. Miller" <davem@...emloft.net>
cc: Eric Dumazet <edumazet@...gle.com>
cc: Jakub Kicinski <kuba@...nel.org>
cc: Paolo Abeni <pabeni@...hat.com>
cc: Jens Axboe <axboe@...nel.dk>
cc: Matthew Wilcox <willy@...radead.org>
cc: linux-nfs@...r.kernel.org
cc: netdev@...r.kernel.org
---
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);
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