Hi,
On Thursday, September 11, 2014 02:42:49 PM Alexander Gordeev wrote:
> The numbers are taken by running 'dd if=/dev/sd{a,b} of=/dev/null'
> in parallel. All time values are in us.
>
> Before this update host lock average holdtime was 2.45 and
> average waittime was 1.24. After the update average holdtime
> dropped to 0.29 (about eight times) while average waittime
> decreased to 0.58 (about two times).
>
> Also, port events are handled with local interrupts enabled
> and compete on individual per-port locks with average holdtime
> 1.25 and average waittime 1.48. So combined average holdtime
> spent while holding host and port locks decreased from 2.45 to
> 0.29 + 1.25 = 1.54 (about 1.6 times).
>
> The downside of this change is introduction of a kernel thread.
>
> The upside is shorter access time to port locks and moving port
> interrupts handling out of the hardware interrupt context.
IMHO it would be great to put the above results into the patch
description (it now looks a bit skimpy).
Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics
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