RE: mmcqd cpu utilization

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> -----Original Message-----
> From: Pierre Ossman [mailto:pierre@xxxxxxxxx]
> Sent: Wednesday, September 02, 2009 12:41 PM
> To: Madhusudhan
> Cc: linux-mmc@xxxxxxxxxxxxxxx; linux-omap@xxxxxxxxxxxxxxx; hch@xxxxxx
> Subject: Re: mmcqd cpu utilization
> 
> On Wed, 2 Sep 2009 12:23:59 -0500
> "Madhusudhan" <madhu.cr@xxxxxx> wrote:
> 
> > Hi,
> >
> > Has anyone monitored the cpu utilization percentage when a MMC/SD card
> is in
> > use? I have noticed that mmc_queue_thread "mmcqd" consumes a lot of cpu
> > cycles in a periodic fashion. What I mean here is that I see spikes of
> high
> > cpu utilization due to mmcqd. There will a cp or similar which will be
> > already consuming cpu to transfer data to the MMC/SD device. Further
> mmcqd
> > increases that load randomly to a high number.
> >
> > Has anyone seen similar behavior? Any thoughts?
> >
> 
> My guess would be that the omap driver doesn't (cannot?) use the
> hardware to wait for busy to end, so the system must poll.
> 
So your guess hints probably at "wait_for_completion(&complete)".
Am I correct?

Regards,
Madhu

> Anything better than that guess will require some profiling. :)
> 
> Rgds
> --
>      -- Pierre Ossman
> 
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