[Intel-gfx] [PATCH 1/3] drm/i915: Limit C-states when waiting for the active request

[Chris Wilson]

Quoting Chris Wilson (2018-07-30 16:25:20)
> If we are waiting for the currently executing request, we have a good
> idea that it will be completed in the very near future and so want to
> cap the CPU_DMA_LATENCY to ensure that we wake up the client quickly.
> 
> v2: Not allowed to block in kmalloc after setting TASK_INTERRUPTIBLE.
> v3: Avoid the blocking notifier as well for TASK_INTERRUPTIBLE
> v4: Beautification?
> v5: And ignore the preemptibility of queue_work before schedule.
> 
> Testcase: igt/gem_sync/store-default
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Eero Tamminen <eero.t.tamminen at intel.com>
> Cc: Francisco Jerez <currojerez at riseup.net>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>

media_bench disagrees with dropping iowait, but agrees with setting the
DMA_LATENCY pm_qos.
-Chris