Commit 89d2d9fb authored by Chuck Lever's avatar Chuck Lever
Browse files

SUNRPC: Revert e0a912e8 



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: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent baabf59c

include/linux/sunrpc/svcsock.h

+0 −2
Original line number Diff line number Diff line
@@ -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;

net/sunrpc/svcsock.c

+0 −6
Original line number Diff line number Diff line
@@ -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 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp) 
		  (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;

}