linux-kernel - Re: [PATCH 0/8] sdhci: Move real work out of an atomic context

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Date:	Wed, 8 Sep 2010 23:05:48 +0100
From:	Chris Ball <cjb@...top.org>
To:	Anton Vorontsov <cbouatmailru@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Wolfram Sang <w.sang@...gutronix.de>,
	Albert Herranz <albert_herranz@...oo.es>,
	Matt Fleming <matt@...sole-pimps.org>,
	Ben Dooks <ben-linux@...ff.org>,
	Pierre Ossman <pierre@...man.eu>, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org
Subject: Re: [PATCH 0/8] sdhci: Move real work out of an atomic context

Hi Anton,

On Thu, Sep 09, 2010 at 01:57:50AM +0400, Anton Vorontsov wrote:
> Thanks!
> 
> Would be also great if you could point out which patch causes
> most of the performance drop (if any)?
> 
> Albert, if you could find time, can you also "bisect" the
> patchset? I wouldn't want to buy Nintendo WII just to debug the
> perf regression. ;-) FWIW, I tried to disable multiblock
> read/writes and test with SD cards, and still didn't notice
> any performance drops.
> 
> Maybe it's SDIO IRQs that cause the performance drop for the
> WII case, as we delay them a little bit? Or it could be the
> patch that introduces threaded IRQ handler in whole causes
> it. If so, I guess we'd need to move some of the processing to
> the real IRQ context, keeping the handler lockless (if
> possible) or introducing a very fine grained locking.

I didn't know anything about a reported performance drop, and I don't
think Andrew did either -- Albert's test results don't seem to have
made it to this list, or anywhere else that I can see.  Could you 
link to/repost his comments?

(I'll be testing with libertas, so that will stress-test SDIO IRQs.)

Thanks,

-- 
Chris Ball   <cjb@...top.org>   <http://printf.net/>
One Laptop Per Child
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