Quoting Tvrtko Ursulin (2018-10-05 09:39:45)
>
> On 05/10/2018 09:03, Chris Wilson wrote:
> > Earlier, we reasoned that having idled the gpu under mempressure, that
> > would be a good time to trim our request slabs in order to perform the
> > next request allocation. We have stopped performing the global operation
> > on the device (no idling) and wish to make the allocation failure
> > handling more local, so out with the global barrier that may take a long
> > time.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/i915_request.c | 11 -----------
> > 1 file changed, 11 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> > index 32bf2c9868bf..c5e40e5f0e65 100644
> > --- a/drivers/gpu/drm/i915/i915_request.c
> > +++ b/drivers/gpu/drm/i915/i915_request.c
> > @@ -657,17 +657,6 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx)
> > if (rq)
> > cond_synchronize_rcu(rq->rcustate);
> >
> > - /*
> > - * We've forced the client to stall and catch up with whatever
> > - * backlog there might have been. As we are assuming that we
> > - * caused the mempressure, now is an opportune time to
> > - * recover as much memory from the request pool as is possible.
> > - * Having already penalized the client to stall, we spend
> > - * a little extra time to re-optimise page allocation.
> > - */
> > - kmem_cache_shrink(i915->requests);
> > - rcu_barrier(); /* Recover the TYPESAFE_BY_RCU pages */
> > -
> > rq = kmem_cache_alloc(i915->requests, GFP_KERNEL);
> > if (!rq) {
> > ret = -ENOMEM;
> >
>
> Wish I was in space...
> .
> .
> .
> .
> ...so no one could hear me scream! :))
I did say I was going to phase it out. I still suspect we need a
cond_synchronize_rcu_expedited(), and the kmem_cache_alloc() may itself
stall for umpteen seconds. But I hope never for igt.
-Chris
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