netdev - Re: RFC: possible NAPI improvements to reduce interrupt rates for low traffic rates

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Message-ID: <46E025CA.50704@katalix.com>
Date:	Thu, 06 Sep 2007 17:07:38 +0100
From:	James Chapman <jchapman@...alix.com>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
CC:	netdev@...r.kernel.org, hadi@...erus.ca, davem@...emloft.net,
	jeff@...zik.org, mandeep.baines@...il.com, ossthema@...ibm.com
Subject: Re: RFC: possible NAPI improvements to reduce interrupt rates for
 low traffic rates

Stephen Hemminger wrote:
> On Thu, 06 Sep 2007 16:30:30 +0100
> James Chapman <jchapman@...alix.com> wrote:
> 
>> Stephen Hemminger wrote:
>>
>>> What about the latency that NAPI imposes? Right now there are certain applications that
>>> don't like NAPI because it add several more microseconds, and this may make it worse.
 >>
>> Latency is something that I think this approach will actually improve, 
>> at the expense of additional polling. Or is it the ksoftirqd scheduling 
>> latency that you are referring to?
> 
> The problem is that you leave interrupts disabled, right.

Are you saying NAPI drivers should avoid keeping interrupts disabled?

> Also you are busy during idle which kills powersaving and no hz clock.

But perhaps some environments don't care about powersave because they 
are always busy? Embedded routers or network servers, for example.

-- 
James Chapman
Katalix Systems Ltd
http://www.katalix.com
Catalysts for your Embedded Linux software development

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