netdev - Re: TCP transmit performance regression

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Message-ID: <CACVXFVPTXB7t=zwkm+HTgDaF3bA02bzff_52S+UAr51PfpvpCg@mail.gmail.com>
Date:	Thu, 5 Jul 2012 16:42:39 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Network Development <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>
Subject: Re: TCP transmit performance regression

On Thu, Jul 5, 2012 at 4:33 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Thu, 2012-07-05 at 16:27 +0800, Ming Lei wrote:
>
>> After some investigation, the problem is caused by enabling
>> DEBUG_SLAB, so it is not a regression.
>>
>
> Strange, unless your machine is a _very_ slow one maybe ?

It is a beagle-xm board, and its cpu is ARMv7, 1GHz.

>
>>
>> Looks no improvement. I still don't know why the window size becomes so
>> small even in good situation(disabling DEBUG_SLAB), and the small
>> window size will cause almost every tcp data packet acked.
>
> You are probably missing the fact that window scaling is enabled.
>
> If you dont post a pcap, I am afraid we cant really help.

See attachment for the pcap trace.


Thanks,
-- 
Ming Lei

Download attachment "tcp.pcap" of type "application/octet-stream" (97922 bytes)