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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Flavio Leitner <fbl@sysclose.org>, netdev@vger.kernel.org
Cc: Paolo Abeni <pabeni@redhat.com>
Subject: Re: Poor TCP performance with XPS enabled after scrubbing skb
Date: Tue, 15 May 2018 14:08:09 -0700	[thread overview]
Message-ID: <c8f6c2f8-c590-2912-c7af-8bce717480b6@gmail.com> (raw)
In-Reply-To: <20180515193128.GA11901@plex.lan>



On 05/15/2018 12:31 PM, Flavio Leitner wrote:
> Hi,
> 
> There is a significant throughput issue (~50% drop) for a single TCP
> stream when the skb is scrubbed and XPS is enabled.
> 
> If I turn CONFIG_XPS off, then the issue never happens and the test
> reaches line rate.  The same happens if I echo 0 to tx-*/xps_cpus.
> 
> It looks like that when the skb is scrubbed, there is no more reference
> to the struct sock, 

And this is really the problem here, since it breaks back pressure (and TCP Small queues)

I am not sure why skb_orphan() is used in this scrubbing really.

  reply	other threads:[~2018-05-15 21:08 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-15 19:31 Poor TCP performance with XPS enabled after scrubbing skb Flavio Leitner
2018-05-15 21:08 ` Eric Dumazet [this message]
2018-05-24 19:17   ` Flavio Leitner
2018-05-25 20:29     ` David Miller

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