[Bug 109830] CPU iowait higher when run the GPU multi decoding threads

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=109830

--- Comment #32 from Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com> ---
(In reply to Owen Zhang from comment #31)
> (In reply to Tvrtko Ursulin from comment #30)
> > (In reply to Owen Zhang from comment #27)
> > > Hi，
> > > 
> > > i have made the following changes on kernel 4.19:
> > > 
> > > 1) apply the following patch:
> > > https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/
> > > ?h=linux-4.20.y&id=0a2fff2428f1e175932dc3cf115b68c868e3a839
> > 
> > This patch makes a difference on it's own? How much?
> > 
> > If it does, I think you have to test by ensuring input data is cached before
> > the timing run, and dump the output to /dev/null.
> > 
> > Otherwise you are accounting for the changes in kernel's block and
> > filesystem subsystems as well.
> > 
> > P.S. I haven't had the time yet to try the repro using the latest
> > instructions.
> 
> only apply this patch, there hasn't any difference. it also need to change
> the io_schedule_timeout to schedule_timeout. 
> 
> both apply these two changes, the cpu iowait number will be down.

So only two changes in conjunction work? Test system is using device mapper?

Can you try pre-caching, a different block device and output to /dev/null?
(Without either patch applied.)

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