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

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Date:	Mon, 2 May 2016 18:16:02 +0200
From:	Jiri Pirko <jiri@...nulli.us>
To:	Eric Dumazet <edumazet@...gle.com>
Cc:	"David S . Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Eric Dumazet <eric.dumazet@...il.com>, eladr@...lanox.com,
	idosch@...lanox.com
Subject: Re: [PATCH net-next 1/2] net: SOCKWQ_ASYNC_NOSPACE optimizations

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.

Thanks.