Hi Trond-
> On Feb 13, 2021, at 3:25 PM, trondmy@xxxxxxxxxx wrote:
>
> From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
>
> 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.
I'm intrigued, but IMO, the patch description needs to explain
why this change should be made. Why abandon Nagle?
If you expect a performance impact, the description should
provide metrics to show it.
(We should have Daire try this change with his multi-client
setup).
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> ---
> include/linux/sunrpc/svcsock.h | 2 ++
> net/sunrpc/svcsock.c | 8 +++++++-
> 2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
> index b7ac7fe68306..bcc555c7ae9c 100644
> --- 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;
Can you take advantage of xpt_mutex: update this field
only in the critical section, and make it a simple
integer type?
> struct page * sk_pages[RPCSVC_MAXPAGES]; /* received data */
> };
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index 5a809c64dc7b..231f510a4830 100644
> --- 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 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp)
> (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) {
> --
> 2.29.2
>
--
Chuck Lever
