drm/i915: Keep a per-engine request pool

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Add a tiny per-engine request mempool so that we should always have a
request available for powermanagement allocations from tricky
contexts. This reserve is expected to be only used for kernel
contexts when barriers must be emitted [almost] without fail.

The main consumer for this reserved request is expected to be engine-pm,
for which we know that there will always be at least the previous pm
request that we can reuse under mempressure (so there should always be
a spare request for engine_park()).

This is an alternative to using a comparatively bulky mempool, which
requires custom handling for both our reserved allocation requirement
and to protect our TYPESAFE_BY_RCU slab cache. The advantage of mempool
would be that it would allow us to keep a larger per-engine request
pool. However, converting over to mempool is straightforward should the
need arise.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-and-tested-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200402184037.21630-1-chris@chris-wilson.co.uk

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This commit is contained in:

Chris Wilson 2020-04-02 19:40:37 +01:00

parent 63d0f3ea8e

commit 43acd6516c

4 changed files with 34 additions and 5 deletions

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7

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

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3

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

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27

drivers/gpu/drm/i915/i915_request.c

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2

drivers/gpu/drm/i915/i915_request.h

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