netdev - Re: BW regression after "tcp: refine TSO autosizing"

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Message-ID: <1421175434.4099.21.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 13 Jan 2015 10:57:14 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Eyal Perry <eyalpe@....mellanox.co.il>
Cc:	netdev@...r.kernel.org, Amir Vadai <amirv@...lanox.com>,
	yevgenyp@...lanox.com, saeedm@...lanox.com, idos@...lanox.com,
	amira@...lanox.com, eyalpe@...lanox.com
Subject: Re: BW regression after "tcp: refine TSO autosizing"

On Tue, 2015-01-13 at 18:48 +0200, Eyal Perry wrote:
> Hello Eric,
> Lately we've observed performance degradation in BW of about 30-40% (depends on
> the setup we use).
> I've bisected the issue down to the this commit: 605ad7f1 ("tcp: refine TSO
> autosizing")
> 
> For instance, I was running the following test:
> 1. Bounding net device' irqs to core 0 for both client and server side
> 2. Running netperf with 64K massage size (used the following command)
> $ netperf -H remote -T 1,1 -l 100 -t TCP_STREAM -- -k THROUGHPUT -M 65536 -m 65536
> 
> I ran the test on upstream net-next including your patch and than reverted it
> and these are the results I got was improvement from 14.6Gbps to 22.1Gbps.
> 
> an additional difference I've noticed when inspecting the ethtool statics,
> number of xmit_more packets increased from 4 to 160 with the reverted kernel.
> 
> We are investigating this issue, do you have a hint?

Which driver are you using for this test ?



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