netdev - Re: [PATCH net-next] tcp: reduce cpu usage when SO

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Message-ID: <1466552914.6850.33.camel@edumazet-glaptop3.roam.corp.google.com>
Date:	Tue, 21 Jun 2016 16:48:34 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jason Baron <jbaron@...mai.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] tcp: reduce cpu usage when SO_SNDBUF is set

On Tue, 2016-06-21 at 11:24 -0400, Jason Baron wrote:

> in tcp_check_space() with something like:
> 
> sk->sk_flags &= ~((1UL << SOCK_QUEUE_SHRUNK) | (1UL << SOCK_SHORT_WRITE));
> 
> Since we are already writing to sk_flags there this should have very
> minimal overhead. And then remove the clear in sk_stream_write_space().

Interesting. You added in 3c7151275c0c9 a smp_mb__after_atomic()
in tcp_check_space(), but there is no atomic operation to begin with ;)