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Subject[PATCH 2.5.21] Make NFS/RPC client use the TCP zero copy API when hardware supports it
From
Date

Does anybody with 'zero copy' compatible networking cards (3c59x,
AceNIC, Tigon3, E1000, ....) notice any performance difference when
using NFS TCP mounts with/without this patch?

Cheers,
Trond

diff -u --recursive --new-file linux-2.5.21/net/sunrpc/xprt.c linux-nfs_zerocopy/net/sunrpc/xprt.c
--- linux-2.5.21/net/sunrpc/xprt.c Fri May 24 13:32:02 2002
+++ linux-nfs_zerocopy/net/sunrpc/xprt.c Sun Jun 16 22:16:22 2002
@@ -67,6 +67,7 @@
#include <net/tcp.h>

#include <asm/uaccess.h>
+#include <linux/pagemap.h>

extern spinlock_t rpc_queue_lock;

@@ -168,6 +169,121 @@
spin_unlock_bh(&xprt->sock_lock);
}

+/* Write an iovec array to a socket */
+static int
+sock_sendkerneliovec(struct socket *sock, struct sockaddr *addr, int addrlen,
+ struct iovec *iov, size_t count, int size)
+{
+ struct msghdr msg = {
+ msg_name: addr,
+ msg_namelen: addrlen,
+ msg_iov: iov,
+ msg_iovlen: count,
+ msg_control: NULL,
+ msg_controllen: 0,
+ msg_flags: MSG_DONTWAIT|MSG_NOSIGNAL,
+ };
+ mm_segment_t oldfs;
+ int ret;
+
+ oldfs = get_fs(); set_fs(get_ds());
+ ret = sock_sendmsg(sock, &msg, size);
+ set_fs(oldfs);
+ return ret;
+}
+
+static int
+xprt_set_cork_sock(struct socket *sock, int val)
+{
+ mm_segment_t oldfs;
+ int ret;
+
+ oldfs = get_fs(); set_fs(get_ds());
+ ret = sock->ops->setsockopt(sock, SOL_TCP, TCP_CORK,
+ (char *)&val, sizeof(val));
+ set_fs(oldfs);
+ return ret;
+}
+
+static inline int
+xprt_cork_sock(struct socket *sock)
+{
+ return xprt_set_cork_sock(sock, 1);
+}
+
+static inline void
+xprt_uncork_sock(struct socket *sock)
+{
+ xprt_set_cork_sock(sock, 0);
+}
+
+/* Send the XDR buffer using the zero copy socket API */
+static int
+xdr_sendpages(struct socket *sock, struct xdr_buf *xdr, size_t base)
+{
+ struct iovec iov;
+ struct page **ppage = xdr->pages;
+ unsigned int len, pglen = xdr->page_len;
+ int err, copied = 0;
+
+ if ((err = xprt_cork_sock(sock)) < 0)
+ return err;
+ len = xdr->head[0].iov_len;
+ if (base < len) {
+ len -= base;
+ iov.iov_len = len;
+ iov.iov_base = (char *)xdr->head[0].iov_base + base;
+ err = sock_sendkerneliovec(sock, NULL, 0, &iov, 1, len);
+ if (err > 0)
+ copied += err;
+ if (err != len)
+ goto out_err;
+ base = 0;
+ } else
+ base -= len;
+ if (base >= pglen) {
+ base -= pglen;
+ goto send_tail;
+ }
+ if (base || xdr->page_base) {
+ pglen -= base;
+ base += xdr->page_base;
+ ppage += base >> PAGE_CACHE_SHIFT;
+ base &= ~PAGE_CACHE_MASK;
+ }
+ do {
+ len = PAGE_CACHE_SIZE;
+ if (base)
+ len -= base;
+ if (pglen < len)
+ len = pglen;
+ err = sock->ops->sendpage(sock, *ppage, base, len, MSG_DONTWAIT);
+ if (err > 0)
+ copied += err;
+ if (err != len)
+ goto out_err;
+ base = 0;
+ ppage++;
+ } while ((pglen -= len) != 0);
+send_tail:
+ len = xdr->tail[0].iov_len;
+ if (len && base < len) {
+ len -= base;
+ iov.iov_len = len;
+ iov.iov_base = (char *)xdr->tail[0].iov_base + base;
+ err = sock_sendkerneliovec(sock, NULL, 0, &iov, 1, len);
+ if (err > 0)
+ copied += err;
+ if (err != len)
+ goto out_err;
+ }
+ xprt_uncork_sock(sock);
+ return copied;
+out_err:
+ xprt_uncork_sock(sock);
+ return copied != 0 ? copied : err;
+}
+
/*
* Write data to socket.
*/
@@ -175,11 +291,8 @@
xprt_sendmsg(struct rpc_xprt *xprt, struct rpc_rqst *req)
{
struct socket *sock = xprt->sock;
- struct msghdr msg;
struct xdr_buf *xdr = &req->rq_snd_buf;
- struct iovec niv[MAX_IOVEC];
- unsigned int niov, slen, skip;
- mm_segment_t oldfs;
+ unsigned int slen, skip;
int result;

if (!sock)
@@ -192,21 +305,16 @@
/* Dont repeat bytes */
skip = req->rq_bytes_sent;
slen = xdr->len - skip;
- niov = xdr_kmap(niv, xdr, skip);
-
- msg.msg_flags = MSG_DONTWAIT|MSG_NOSIGNAL;
- msg.msg_iov = niv;
- msg.msg_iovlen = niov;
- msg.msg_name = (struct sockaddr *) &xprt->addr;
- msg.msg_namelen = sizeof(xprt->addr);
- msg.msg_control = NULL;
- msg.msg_controllen = 0;
-
- oldfs = get_fs(); set_fs(get_ds());
- result = sock_sendmsg(sock, &msg, slen);
- set_fs(oldfs);

- xdr_kunmap(xdr, skip);
+ if (xdr->page_len == 0 || !xprt->stream) {
+ struct iovec niv[MAX_IOVEC];
+ unsigned int niov;
+ niov = xdr_kmap(niv, xdr, skip);
+ result = sock_sendkerneliovec(sock, (struct sockaddr *)&xprt->addr,
+ sizeof(xprt->addr), niv, niov, slen);
+ xdr_kunmap(xdr, skip);
+ } else
+ result = xdr_sendpages(sock, xdr, skip);

dprintk("RPC: xprt_sendmsg(%d) = %d\n", slen, result);

-
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