From: Stephen Hemminger <shemminger@linux-foundation.org>
To: James Chapman <jchapman@katalix.com>
Cc: netdev@vger.kernel.org, hadi@cyberus.ca, davem@davemloft.net,
jeff@garzik.org, mandeep.baines@gmail.com, ossthema@de.ibm.com
Subject: Re: RFC: possible NAPI improvements to reduce interrupt rates for low traffic rates
Date: Thu, 6 Sep 2007 16:37:03 +0100 [thread overview]
Message-ID: <20070906163703.4fc12d32@oldman> (raw)
In-Reply-To: <46E01D16.5000609@katalix.com>
On Thu, 06 Sep 2007 16:30:30 +0100
James Chapman <jchapman@katalix.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. Also you are busy during
idle which kills powersaving and no hz clock.
> > Maybe a per-device flag or tuning parameters (like weight sysfs value)? or some other
> > way to set low-latency values.
>
> Yes. I'd like to think good defaults could be derived though, perhaps
> based on settings like CONFIG_PREEMPT, CONFIG_HIGH_RES_TIMER, CONFIG_HZ
> and maybe even bogomips / nr_cpus.
>
> --
> James Chapman
> Katalix Systems Ltd
> http://www.katalix.com
> Catalysts for your Embedded Linux software development
>
next prev parent reply other threads:[~2007-09-06 15:37 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-06 14:16 RFC: possible NAPI improvements to reduce interrupt rates for low traffic rates James Chapman
2007-09-06 14:37 ` Stephen Hemminger
2007-09-06 15:30 ` James Chapman
2007-09-06 15:37 ` Stephen Hemminger [this message]
2007-09-06 16:07 ` James Chapman
2007-09-06 23:06 ` jamal
2007-09-07 9:31 ` James Chapman
2007-09-07 13:22 ` jamal
2007-09-10 9:20 ` James Chapman
2007-09-10 12:27 ` jamal
2007-09-12 7:04 ` Bill Fink
2007-09-12 12:12 ` jamal
2007-09-12 13:50 ` James Chapman
2007-09-12 14:02 ` Stephen Hemminger
2007-09-12 16:26 ` James Chapman
2007-09-12 16:47 ` Mandeep Baines
2007-09-13 6:57 ` David Miller
2007-09-14 13:14 ` jamal
2007-09-07 21:20 ` Jason Lunz
2007-09-10 9:25 ` James Chapman
2007-09-07 3:55 ` Mandeep Singh Baines
2007-09-07 9:38 ` James Chapman
2007-09-08 16:42 ` Mandeep Singh Baines
2007-09-10 9:33 ` James Chapman
2007-09-10 12:12 ` jamal
2007-09-08 16:32 ` Andi Kleen
2007-09-10 9:25 ` James Chapman
2007-09-12 15:12 ` David Miller
2007-09-12 16:39 ` James Chapman
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