Massive power regression going 3.4->3.5

[Chris Wilson]

On Wed, 01 Aug 2012 09:45:04 +0100, James Bottomley <James.Bottomley at 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 at 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, and follow up with a new pair
of /sys/kernel/debug/dri/0/i915_cur_delayinfo and .../i915_drpc_info.

This will let us see whether the pm counters are truly advancing and
what activity the driver is performing whilst idle.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre