SUNRPC: Use TCP_CORK to optimise send performance on the server

Use a counter to keep track of how many requests are queued behind the
xprt->xpt_mutex, and keep TCP_CORK set until the queue is empty.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Link: https://lore.kernel.org/linux-nfs/20210213202532.23146-1-trondmy@kernel.org/T/#u
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
index b7ac7fe..bcc555c 100644 (file)
--- a/include/linux/sunrpc/svcsock.h
+++ b/include/linux/sunrpc/svcsock.h
@@ -35,6 +35,8 @@ struct svc_sock {
        /* Total length of the data (not including fragment headers)
         * received so far in the fragments making up this rpc: */
        u32                     sk_datalen;
+       /* Number of queued send requests */
+       atomic_t                sk_sendqlen;
 
        struct page *           sk_pages[RPCSVC_MAXPAGES];      /* received data */
 };

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 5a809c6..231f510 100644 (file)
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1171,18 +1171,23 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp)
 
        svc_tcp_release_rqst(rqstp);
 
+       atomic_inc(&svsk->sk_sendqlen);
        mutex_lock(&xprt->xpt_mutex);
        if (svc_xprt_is_dead(xprt))
                goto out_notconn;
+       tcp_sock_set_cork(svsk->sk_sk, true);
        err = svc_tcp_sendmsg(svsk->sk_sock, &msg, xdr, marker, &sent);
        xdr_free_bvec(xdr);
        trace_svcsock_tcp_send(xprt, err < 0 ? err : sent);
        if (err < 0 || sent != (xdr->len + sizeof(marker)))
                goto out_close;
+       if (atomic_dec_and_test(&svsk->sk_sendqlen))
+               tcp_sock_set_cork(svsk->sk_sk, false);
        mutex_unlock(&xprt->xpt_mutex);
        return sent;
 
 out_notconn:
+       atomic_dec(&svsk->sk_sendqlen);
        mutex_unlock(&xprt->xpt_mutex);
        return -ENOTCONN;
 out_close:
@@ -1192,6 +1197,7 @@ out_close:
                  (err < 0) ? err : sent, xdr->len);
        set_bit(XPT_CLOSE, &xprt->xpt_flags);
        svc_xprt_enqueue(xprt);
+       atomic_dec(&svsk->sk_sendqlen);
        mutex_unlock(&xprt->xpt_mutex);
        return -EAGAIN;
 }
@@ -1261,7 +1267,7 @@ static void svc_tcp_init(struct svc_sock *svsk, struct svc_serv *serv)
                svsk->sk_datalen = 0;
                memset(&svsk->sk_pages[0], 0, sizeof(svsk->sk_pages));
 
-               tcp_sk(sk)->nonagle |= TCP_NAGLE_OFF;
+               tcp_sock_set_nodelay(sk);
 
                set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
                switch (sk->sk_state) {