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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Rick Jones <rick.jones2@hp.com>
Cc: David Miller <davem@davemloft.net>,
	netdev <netdev@vger.kernel.org>,
	Yuchung Cheng <ycheng@google.com>,
	Neal Cardwell <ncardwell@google.com>,
	Michael Kerrisk <mtk.manpages@gmail.com>
Subject: Re: [PATCH v3 net-next 2/2] tcp: TCP_NOTSENT_LOWAT socket option
Date: Tue, 23 Jul 2013 09:48:18 -0700	[thread overview]
Message-ID: <1374598098.3449.39.camel@edumazet-glaptop> (raw)
In-Reply-To: <51EEAD54.2040603@hp.com>

On Tue, 2013-07-23 at 09:20 -0700, Rick Jones wrote:

> Right - I am questioning whether it is worth the CPU increase.

There is no cpu increase for common workloads, and hosts can save GB of
precious memory thanks to this patch.

There is a cpu increase only for 'netperf' kind of program, relying on
blocking sendmsg() and using one thread per socket, _if_ and only _if_
they set a crazy notsent_lowat value.

Remember I forced nobody to do that. Its like forcing SO_SNDBUF with one
byte, and SO_RCVBUF with one byte, and expecting good line rate
performance !

This patch changes the threshold to get the 'socket is writeable'
POLLOUT event, and avoid filling socket write queues with too many
packets.

Like all thresholds, it has to be properly used.

  reply	other threads:[~2013-07-23 16:48 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-23  3:27 Eric Dumazet
2013-07-23  3:52 ` Hannes Frederic Sowa
2013-07-23 15:26 ` Rick Jones
2013-07-23 15:44   ` Eric Dumazet
2013-07-23 16:20     ` Rick Jones
2013-07-23 16:48       ` Eric Dumazet [this message]
2013-07-23 17:18       ` Eric Dumazet
2013-07-23 18:24 ` Yuchung Cheng
2013-07-25  0:55 ` David Miller
2013-07-23 19:19 Neal Cardwell
2013-07-23 19:28 Neal Cardwell

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