drm/i915/execlists: Minimalistic timeslicing

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If we have multiple contexts of equal priority pending execution,
activate a timer to demote the currently executing context in favour of
the next in the queue when that timeslice expires. This enforces
fairness between contexts (so long as they allow preemption -- forced
preemption, in the future, will kick those who do not obey) and allows
us to avoid userspace blocking forward progress with e.g. unbounded
MI_SEMAPHORE_WAIT.

For the starting point here, we use the jiffie as our timeslice so that
we should be reasonably efficient wrt frequent CPU wakeups.

Testcase: igt/gem_exec_scheduler/semaphore-resolve
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190620142052.19311-2-chris@chris-wilson.co.uk

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This commit is contained in:

Chris Wilson 2019-06-20 15:20:52 +01:00

parent 22b7a426bb

commit 8ee36e048c

5 changed files with 347 additions and 0 deletions

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6

drivers/gpu/drm/i915/gt/intel_engine_types.h

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116

drivers/gpu/drm/i915/gt/intel_lrc.c

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drivers/gpu/drm/i915/gt/selftest_lrc.c

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drivers/gpu/drm/i915/i915_scheduler.c

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drivers/gpu/drm/i915/i915_scheduler_types.h

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