SUNRPC: Revert e0a912e8ddba

Flamegraph analysis showed that the cork/uncork calls consume
nearly a third of the CPU time spent in svc_tcp_sendto(). The
other two consumers are mutex lock/unlock and svc_tcp_sendmsg().

Now that svc_tcp_sendto() coalesces RPC messages properly, there
is no need to introduce artificial delays to prevent sending
partial messages.

After applying this change, I measured a 1.2K read IOPS increase
for 8KB random I/O (several percent) on 56Gb IP over IB.

Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
index caf3308..a7ea544 100644 (file)
--- a/include/linux/sunrpc/svcsock.h
+++ b/include/linux/sunrpc/svcsock.h
@@ -35,8 +35,6 @@ 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_frag_cache  sk_frag_cache;
 

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 2ff7303..8db8227 100644 (file)
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1268,22 +1268,17 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp)
        svc_tcp_release_ctxt(xprt, rqstp->rq_xprt_ctxt);
        rqstp->rq_xprt_ctxt = NULL;
 
-       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, rqstp, marker, &sent);
        trace_svcsock_tcp_send(xprt, err < 0 ? (long)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:
@@ -1292,7 +1287,6 @@ out_close:
                  (err < 0) ? "got error" : "sent",
                  (err < 0) ? err : sent, xdr->len);
        svc_xprt_deferred_close(xprt);
-       atomic_dec(&svsk->sk_sendqlen);
        mutex_unlock(&xprt->xpt_mutex);
        return -EAGAIN;
 }