netdev - Re: [RFC] napi: limit GRO latency

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Message-ID: <20121008121248.783e6dc4@nehalam.linuxnetplumber.net>
Date:	Mon, 8 Oct 2012 12:12:48 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	David Miller <davem@...emloft.net>
Cc:	eric.dumazet@...il.com, rick.jones2@...com,
	herbert@...dor.apana.org.au, netdev@...r.kernel.org,
	jesse@...ira.com
Subject: Re: [RFC] napi: limit GRO latency

On Mon, 08 Oct 2012 15:10:35 -0400 (EDT)
David Miller <davem@...emloft.net> wrote:

> From: Stephen Hemminger <shemminger@...tta.com>
> Date: Mon, 8 Oct 2012 11:58:35 -0700
> 
> > Limit the latency of pending GRO in NAPI processing to 2*HZ.
> > When the system is under heavy network load, NAPI will go into
> > poll mode via soft irq, and only stay in the loop for
> > two jiffies. If this occurs, process the GRO pending list
> > to make sure and not delay outstanding TCP frames for too long.
> > 
> > Rearrange the exit path to get rid of unnecessary goto logic.
> > 
> > Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
> 
> Did you see Eric's patch I just applied which limits it to 1ms?

Think this is a different problem.
After leaving softirq, it may be a long time until
ksoftirqd is run which is a different problem.
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