[PATCH] RPC: Reduce stack utilization in xs_sendpages

 Reduce stack utilization of the RPC socket transport's send path.

 A couple of unlikely()s are added to ensure the compiler places the
 tail processing at the end of the csect.

 Test-plan:
 Millions of fsx operations.  Performance characterization such as "sio" or
 "iozone".

 Version: Thu, 11 Aug 2005 16:04:30 -0400

 Signed-off-by: Chuck Lever <cel@netapp.com>
 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 43 insertions, 30 deletions

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 80222de3afa4..a5a04203a6b0 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -68,6 +68,41 @@ static inline void xs_pktdump(char *msg, u32 *packet, unsigned int count)
 }
 #endif
 
+#define XS_SENDMSG_FLAGS        (MSG_DONTWAIT | MSG_NOSIGNAL)
+
+static inline int xs_send_head(struct socket *sock, struct sockaddr *addr, int addrlen, struct xdr_buf *xdr, unsigned int base, unsigned int len)
+{
+        struct kvec iov = {
+                .iov_base       = xdr->head[0].iov_base + base,
+                .iov_len        = len - base,
+        };
+        struct msghdr msg = {
+                .msg_name       = addr,
+                .msg_namelen    = addrlen,
+                .msg_flags      = XS_SENDMSG_FLAGS,
+        };
+
+        if (xdr->len > len)
+                msg.msg_flags |= MSG_MORE;
+
+        if (likely(iov.iov_len))
+                return kernel_sendmsg(sock, &msg, &iov, 1, iov.iov_len);
+        return kernel_sendmsg(sock, &msg, NULL, 0, 0);
+}
+
+static int xs_send_tail(struct socket *sock, struct xdr_buf *xdr, unsigned int base, unsigned int len)
+{
+        struct kvec iov = {
+                .iov_base       = xdr->tail[0].iov_base + base,
+                .iov_len        = len - base,
+        };
+        struct msghdr msg = {
+                .msg_flags      = XS_SENDMSG_FLAGS,
+        };
+
+        return kernel_sendmsg(sock, &msg, &iov, 1, iov.iov_len);
+}
+
 /**
  * xs_sendpages - write pages directly to a socket
  * @sock: socket to send on
@@ -77,7 +112,7 @@ static inline void xs_pktdump(char *msg, u32 *packet, unsigned int count)
  * @base: starting position in the buffer
  *
  */
-static int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen, struct xdr_buf *xdr, unsigned int base, int msgflags)
+static int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen, struct xdr_buf *xdr, unsigned int base)
 {
         struct page **ppage = xdr->pages;
         unsigned int len, pglen = xdr->page_len;
@@ -86,35 +121,20 @@ static int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen,
 
         len = xdr->head[0].iov_len;
         if (base < len || (addr != NULL && base == 0)) {
-                struct kvec iov = {
-                        .iov_base = xdr->head[0].iov_base + base,
-                        .iov_len  = len - base,
-                };
-                struct msghdr msg = {
-                        .msg_name    = addr,
-                        .msg_namelen = addrlen,
-                        .msg_flags   = msgflags,
-                };
-                if (xdr->len > len)
-                        msg.msg_flags |= MSG_MORE;
-
-                if (iov.iov_len != 0)
-                        err = kernel_sendmsg(sock, &msg, &iov, 1, iov.iov_len);
-                else
-                        err = kernel_sendmsg(sock, &msg, NULL, 0, 0);
+                err = xs_send_head(sock, addr, addrlen, xdr, base, len);
                 if (ret == 0)
                         ret = err;
                 else if (err > 0)
                         ret += err;
-                if (err != iov.iov_len)
+                if (err != (len - base))
                         goto out;
                 base = 0;
         } else
                 base -= len;
 
-        if (pglen == 0)
+        if (unlikely(pglen == 0))
                 goto copy_tail;
-        if (base >= pglen) {
+        if (unlikely(base >= pglen)) {
                 base -= pglen;
                 goto copy_tail;
         }
@@ -127,7 +147,7 @@ static int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen,
 
         sendpage = sock->ops->sendpage ? : sock_no_sendpage;
         do {
-                int flags = msgflags;
+                int flags = XS_SENDMSG_FLAGS;
 
                 len = PAGE_CACHE_SIZE;
                 if (base)
@@ -154,14 +174,7 @@ static int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen,
 copy_tail:
         len = xdr->tail[0].iov_len;
         if (base < len) {
-                struct kvec iov = {
-                        .iov_base = xdr->tail[0].iov_base + base,
-                        .iov_len  = len - base,
-                };
-                struct msghdr msg = {
-                        .msg_flags   = msgflags,
-                };
-                err = kernel_sendmsg(sock, &msg, &iov, 1, iov.iov_len);
+                err = xs_send_tail(sock, xdr, base, len);
                 if (ret == 0)
                         ret = err;
                 else if (err > 0)
@@ -202,7 +215,7 @@ static int xs_sendmsg(struct rpc_xprt *xprt, struct rpc_rqst *req)
         skip = req->rq_bytes_sent;
 
         clear_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
-        result = xs_sendpages(sock, addr, addrlen, xdr, skip, MSG_DONTWAIT);
+        result = xs_sendpages(sock, addr, addrlen, xdr, skip);
 
         dprintk("RPC:      xs_sendmsg(%d) = %d\n", xdr->len - skip, result);