From: Eric Dumazet <eric.dumazet@gmail.com>
To: Rick Jones <rick.jones2@hp.com>
Cc: David Miller <davem@davemloft.net>,
netdev@vger.kernel.org, therbert@google.com,
ncardwell@google.com, maze@google.com, ycheng@google.com,
ilpo.jarvinen@helsinki.fi
Subject: Re: [PATCH 2/2 net-next] tcp: sk_add_backlog() is too agressive for TCP
Date: Tue, 24 Apr 2012 00:05:07 +0200 [thread overview]
Message-ID: <1335218707.5205.87.camel@edumazet-glaptop> (raw)
In-Reply-To: <4F95CECF.6030901@hp.com>
On Mon, 2012-04-23 at 14:51 -0700, Rick Jones wrote:
> On 04/23/2012 02:30 PM, Eric Dumazet wrote:
> > Yet, in the small time it takes to perform this operation, softirq can
> > queue up to 300 packets coming from the other side.
>
> There is more to it than just queue-up 16 KB right?
At full rate, we send 825.000 packets per second, and should receive
412.000 ACKS per second if receiver is standard TCP.
The ACK are not smooth, because receiver also have a huge backlog issue
and can send train of ACKS. (I have seen backlogs on receiver using more
than 500 us to be processed)
If the copyin(16KB) from user to kernel takes some us (preempt,
irqs...), its pretty easy to catch an ACK train in this window.
next prev parent reply other threads:[~2012-04-23 22:05 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-23 9:38 [PATCH 2/2 net-next] tcp: sk_add_backlog() is too agressive for TCP Eric Dumazet
2012-04-23 17:14 ` Rick Jones
2012-04-23 17:23 ` Eric Dumazet
2012-04-23 20:01 ` David Miller
2012-04-23 20:37 ` Eric Dumazet
2012-04-23 20:57 ` Rick Jones
2012-04-23 21:30 ` Eric Dumazet
2012-04-23 21:51 ` Rick Jones
2012-04-23 21:56 ` Rick Jones
2012-04-23 22:05 ` Eric Dumazet [this message]
2012-04-23 22:16 ` Rick Jones
2012-04-24 15:25 ` Christoph Lameter
2012-04-23 21:01 ` David Miller
2012-04-23 21:38 ` Eric Dumazet
2012-04-24 2:20 ` Eric Dumazet
2012-04-24 2:27 ` David Miller
2012-04-24 8:01 ` Ilpo Järvinen
2012-04-24 8:10 ` David Miller
2012-04-24 8:21 ` Ilpo Järvinen
2012-04-24 8:25 ` David Miller
2012-04-24 8:40 ` Ilpo Järvinen
2012-04-24 8:48 ` David Miller
2012-04-24 10:32 ` Ilpo Järvinen
2012-04-24 8:56 ` Eric Dumazet
2012-04-26 8:10 ` [RFC] allow skb->head to point/alias to first skb frag Eric Dumazet
2012-04-26 8:36 ` David Miller
2012-04-26 9:10 ` Eric Dumazet
2012-04-26 9:18 ` David Miller
2012-04-26 9:22 ` Eric Dumazet
2012-04-26 10:09 ` Maciej Żenczykowski
2012-04-26 12:32 ` Eric Dumazet
2012-04-26 13:50 ` Eric Dumazet
2012-04-26 20:12 ` David Miller
2012-04-26 20:18 ` Eric Dumazet
2012-04-24 8:49 ` [PATCH 2/2 net-next] tcp: sk_add_backlog() is too agressive for TCP Eric Dumazet
2012-04-24 8:44 ` David Laight
2012-04-24 8:53 ` Eric Dumazet
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