From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Pirko Subject: Re: [PATCH net-next 1/2] net: SOCKWQ_ASYNC_NOSPACE optimizations Date: Mon, 2 May 2016 22:45:44 +0200 Message-ID: <20160502204544.GA2349@nanopsycho.orion> References: <1461605974-4242-1-git-send-email-edumazet@google.com> <1461605974-4242-2-git-send-email-edumazet@google.com> <20160502161602.GA1984@nanopsycho.orion> <1462206138.5535.255.camel@edumazet-glaptop3.roam.corp.google.com> <20160502191229.GA1946@nanopsycho.orion> <1462220607.5535.273.camel@edumazet-glaptop3.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eric Dumazet , "David S . Miller" , netdev , eladr@mellanox.com, idosch@mellanox.com To: Eric Dumazet Return-path: Received: from mail-wm0-f65.google.com ([74.125.82.65]:35708 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755143AbcEBUpr (ORCPT ); Mon, 2 May 2016 16:45:47 -0400 Received: by mail-wm0-f65.google.com with SMTP id e201so477110wme.2 for ; Mon, 02 May 2016 13:45:47 -0700 (PDT) Content-Disposition: inline In-Reply-To: <1462220607.5535.273.camel@edumazet-glaptop3.roam.corp.google.com> Sender: netdev-owner@vger.kernel.org List-ID: Mon, May 02, 2016 at 10:23:27PM CEST, eric.dumazet@gmail.com wrote: >On Mon, 2016-05-02 at 21:12 +0200, Jiri Pirko wrote: >> Mon, May 02, 2016 at 06:22:18PM CEST, eric.dumazet@gmail.com wrote: >> >On Mon, 2016-05-02 at 18:16 +0200, Jiri Pirko wrote: >> >> Mon, Apr 25, 2016 at 07:39:32PM CEST, edumazet@google.com wrote: >> >> >SOCKWQ_ASYNC_NOSPACE is tested in sock_wake_async() >> >> >so that a SIGIO signal is sent when needed. >> >> > >> >> >tcp_sendmsg() clears the bit. >> >> >tcp_poll() sets the bit when stream is not writeable. >> >> > >> >> >We can avoid two atomic operations by first checking if socket >> >> >is actually interested in the FASYNC business (most sockets in >> >> >real applications do not use AIO, but select()/poll()/epoll()) >> >> > >> >> >This also removes one cache line miss to access sk->sk_wq->flags >> >> >in tcp_sendmsg() >> >> > >> >> >Signed-off-by: Eric Dumazet >> >> >> >> I just bisected down to this. This is causing a regression for me when >> >> my nfs mount becomes stuck. I can easily reproduce this if you need to >> >> test the fix. >> > >> >What do you mean by 'when nfs mount becomes stuck' ? >> > >> >Is this patch making nfs not functional , or does it make recovery from >> >some nfs error bad ? >> >> I can mount nfs on the host. But when I do something (compile a kernel >> module in my case), it gets stuck. Then I cannot even ssh to the machine. >> No messages in dmesg. I didn't debug it any further. I just bisected and >> verified that this patch caused this behaviour. > >Interesting. > >It looks like net/sunrpc/xprtsock.c should set SOCK_FASYNC >even if it is not actually using fasync_list > >Could you try this quick hack to check if this is the right way ? Yep, works, I do not see the issue with this patch anymore. Thanks. > >Thanks ! > >diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c >index a6c68dc086af83233ee315642638f4a1990ee622..b90c5397b5e137c6cc8accad6eebe2b876363d4e 100644 >--- a/net/sunrpc/xprtsock.c >+++ b/net/sunrpc/xprtsock.c >@@ -1950,6 +1950,7 @@ static int xs_local_finish_connecting(struct rpc_xprt *xprt, > sk->sk_user_data = xprt; > sk->sk_data_ready = xs_data_ready; > sk->sk_write_space = xs_udp_write_space; >+ sock_set_flag(sk, SOCK_FASYNC); > sk->sk_error_report = xs_error_report; > sk->sk_allocation = GFP_NOIO; > >@@ -2136,6 +2137,7 @@ static void xs_udp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock) > sk->sk_user_data = xprt; > sk->sk_data_ready = xs_data_ready; > sk->sk_write_space = xs_udp_write_space; >+ sock_set_flag(sk, SOCK_FASYNC); > sk->sk_allocation = GFP_NOIO; > > xprt_set_connected(xprt); >@@ -2237,6 +2239,7 @@ static int xs_tcp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock) > sk->sk_data_ready = xs_tcp_data_ready; > sk->sk_state_change = xs_tcp_state_change; > sk->sk_write_space = xs_tcp_write_space; >+ sock_set_flag(sk, SOCK_FASYNC); > sk->sk_error_report = xs_error_report; > sk->sk_allocation = GFP_NOIO; > > >