> -----Original Message-----
> From: Chris Ball [mailto:[email protected]]
> Sent: Wednesday, April 11, 2012 12:08 AM
> To: Subhash Jadavani
> Cc: [email protected]; [email protected]
> Subject: Re: [PATCH v1 1/1] mmc: block: replace __blk_end_request() with
> blk_end_request()
>
> Hi,
>
> On Tue, Apr 10 2012, Subhash Jadavani wrote:
> > This patch replaces all __blk_end_request() calls with
> > blk_end_request() and __blk_end_request_all() calls with
> > blk_end_request_all().
> >
> > Testing done: 20 process concurrent read/write on sd card and eMMC.
> > Ran this test for almost a day on multicore system and no errors
> > observed.
>
> Is there a measurable improvement in throughput or latency that you can
show
> data for?
This change was not meant for improving MMC throughput; it's basically about
becoming fair to other threads/interrupts in the system. By holding spin
lock and interrupts disabled for longer duration, we won't allow other
threads/interrupts to run at all.
Actually slight performance degradation at file system level can be expected
as we are not holding the spin lock during blk_update_bidi_request() which
means our mmcqd thread may get preempted for other high priority thread or
any interrupt in the system.
These are performance numbers (100MB file write) with eMMC running in DDR
mode:
Without this patch:
Name of the Test Value Unit
LMDD Read Test 53.79 MBPS
LMDD Write Test 18.86 MBPS
IOZONE Read Test 51.65 MBPS
IOZONE Write Test 24.36 MBPS
With this patch:
Name of the Test Value Unit
LMDD Read Test 52.94 MBPS
LMDD Write Test 16.70 MBPS
IOZONE Read Test 52.08 MBPS
IOZONE Write Test 23.29 MBPS
Read numbers are fine. Write numbers are bit down (especially LMDD write),
may be because write requests normally have large transfer size and which
means there are chances that while mmcq is executing
blk_update_bidi_request(), it may get interrupted by interrupts or other
high priority thread.
Regards,
Subhash
>
> Thanks,
>
> - Chris.
> --
> Chris Ball <[email protected]> <http://printf.net/>
> One Laptop Per Child
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