linux-kernel - Re: [PATCH 0/5] Reduce cross CPU IPI interference

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Message-ID: <4E887C23.4030600@tilera.com>
Date:	Sun, 2 Oct 2011 10:58:43 -0400
From:	Chris Metcalf <cmetcalf@...era.com>
To:	Gilad Ben-Yossef <gilad@...yossef.com>
CC:	<linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Russell King <linux@....linux.org.uk>, <linux-mm@...ck.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>
Subject: Re: [PATCH 0/5] Reduce cross CPU IPI interference

On 10/2/2011 4:44 AM, Gilad Ben-Yossef wrote:
>> We have some code in our tree (not yet
>> returned to the community) that tries to deal with some sources of interrupt
>> jitter on tiles that are running isolcpu and want to be 100% in user space.
> Yes, I think this work will benefit this kind of use case (CPU/user
> space bound on a dedicated CPU)
> the most, although other use cases can benefit as well (e.g. power
> management with idle cores).
>
> Btw, do you have any plan to share the patches you mentioned? it could
> save me a lot of time. Not wanting to
> re-invent the wheel and all that...

I'd like to, but getting the patch put together cleanly is still on my list
behind a number of other things (glibc community return, kernel catch-up
with a backlog of less controversial changes, customer crises, enhancements
targeted to forthcoming releases, etc.; I'm sure you know the drill...)

>>> This first version creates an on_each_cpu_mask infrastructure API (derived
>>> from
>>> existing arch specific versions in Tile and Arm) and uses it to turn two
>>> global
>>> IPI invocation to per CPU group invocations.
>> The global version looks fine; I would probably make on_each_cpu() an inline
>> in the !SMP case now that you are (correctly, I suspect) disabling
>> interrupts when calling the function.
>>
> Good point. Will do.
>
> I will take this email as an ACK to the tile relevant changes, if that
> is OK with you.

Yes, definitely.

Acked-by: Chris Metcalf <cmetcalf@...era.com>

-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com

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