Re: Massive power regression going 3.4->3.5

[Chris Wilson <chris@chris-wilson.co.uk>]

On Wed, 01 Aug 2012 10:38:36 +0100, James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> On Wed, 2012-08-01 at 09:58 +0100, Chris Wilson wrote:
> > On Wed, 01 Aug 2012 09:45:04 +0100, James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> > > On Wed, 2012-08-01 at 09:16 +0100, Chris Wilson wrote:
> > > > On Wed, 01 Aug 2012 09:06:12 +0100, James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> > > > > I got the attached to apply and it doesn't really improve the idle power
> > > > > much (12.5W).
> > > > 
> > > > That's good to know. Next step is to try overriding i915.semaphores.
> > > > Can you please test with i915.semaphores=0 and i915.semaphores=1?
> > > 
> > > There's not much point doing i915_semaphores=1 since that's the default
> > > on gen 6 hardware, but i915_semaphores=0 recovers and idle power of
> > > ~6.5W
> > 
> > It is only the default if iommu is off, and changing the default
> > was one of the side-effects of the patch you bisected.
> > 
> > Can you please login to the desktop, let it idle, record
> > /sys/kernel/debug/dri/0/i915_cur_delayinfo and .../i915_drpc_info.
> > Then trace-cmd record -e i915 sleep 10s,
> 
> OK, what is trace-cmd?  It looks similar to perf tools ... is that it?

Yes, it is roughly equivalent and you should be able to achieve the same
with perf trace - except I haven't done it before so I don't have quick
advice on how to drive it. :)
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre