[Intel-gfx] [PATCH v3] drm/i915: Queue page flip work via a low latency, unbound workqueue

[Maarten Lankhorst]

Op 20-09-16 om 14:51 schreef Chris Wilson:
> On Tue, Sep 20, 2016 at 02:58:19PM +0300, Imre Deak wrote:
>> While user space has control over the scheduling priority of its page
>> flipping thread, the corresponding work the driver schedules for MMIO
>> flips always runs from the generic system workqueue which has some
>> scheduling overhead due it being CPU bound. This would hinder an
>> application that wants more stringent guarantees over flip timing (to
>> avoid missing a flip at the next frame count).
>>
>> Fix this by scheduling the work from the unbound system workqueue
>> which provides for minimal scheduling latency.
>>
>> v2:
>> - Use an unbound workqueue instead of a high-prio one. (Tvrtko, Chris)
>> v3:
>> - Use the system unbound wq instead of a dedicated one. (Maarten)
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97775
>> Testcase: igt/kms_cursor_legacy
>> CC: Chris Wilson <chris at chris-wilson.co.uk>
>> CC: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
>> CC: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>> Signed-off-by: Imre Deak <imre.deak at intel.com>
>> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com> (v1)
> We violate the unbound_wq rules no worse than the ordinary system_wq,
> and this brings mmioflip on a par with nonblocking atomic modesets, so
> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
> -Chris
>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>