netdev - Re: Throughput regression with `tcp: refine TSO autosizing`

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Message-ID: <1423233346.31870.136.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Fri, 06 Feb 2015 06:35:46 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Michal Kazior <michal.kazior@...to.com>
Cc:	Neal Cardwell <ncardwell@...gle.com>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	Eyal Perry <eyalpe@....mellanox.co.il>
Subject: Re: Throughput regression with `tcp: refine TSO autosizing`

On Fri, 2015-02-06 at 15:08 +0100, Michal Kazior wrote:

> Hmm.. I confirm it works. However the value at which I get full rate
> on a single flow is more than 2048K. Also using non-default
> wmem_default seems to introduce packet loss as per iperf reports at
> the receiver. I suppose this is kind of expected but on the other hand
> wmem_default=262992 and 5 flows of UDP max the device out with 0
> packet loss.

If you increase ability to flood on one flow, then you need to make sure
receiver has big rcvbuf as well.

echo 2000000 >/proc/sys/net/core/rmem_default

Otherwise it might drop bursts.

This is the kind of things that TCP does automatically, not UDP.


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