netdev - Re: [PATCH net-next 1/2] net: SOCKWQ_ASYNC

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Message-ID: <1462206138.5535.255.camel@edumazet-glaptop3.roam.corp.google.com>
Date:	Mon, 02 May 2016 09:22:18 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	Eric Dumazet <edumazet@...gle.com>,
	"David S . Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>, eladr@...lanox.com,
	idosch@...lanox.com
Subject: Re: [PATCH net-next 1/2] net: SOCKWQ_ASYNC_NOSPACE optimizations

On Mon, 2016-05-02 at 18:16 +0200, Jiri Pirko wrote:
> Mon, Apr 25, 2016 at 07:39:32PM CEST, edumazet@...gle.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 <edumazet@...gle.com>
> 
> 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 ?

Thanks.