Under mempressure, our goal is to allow ourselves sufficient time to
reclaim the RCU protected slabs without overly penalizing our clients.
Currently, we use a 1 jiffie wait if the client is still active as a
means of throttling the allocations, but we can instead wait for the end
of the RCU grace period of the clients previous allocation.
Suggested-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
drivers/gpu/drm/i915/i915_request.c | 14 ++++++--------
drivers/gpu/drm/i915/i915_request.h | 8 ++++++++
2 files changed, 14 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 72bcb4ca0c45..a492385b2089 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -732,17 +732,13 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx)
rq = kmem_cache_alloc(i915->requests,
GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
if (unlikely(!rq)) {
+ i915_retire_requests(i915);
+
/* Ratelimit ourselves to prevent oom from malicious clients */
rq = i915_gem_active_raw(&ce->ring->timeline->last_request,
&i915->drm.struct_mutex);
- if (rq && i915_request_wait(rq,
- I915_WAIT_LOCKED |
- I915_WAIT_INTERRUPTIBLE,
- 1) == -EINTR) {
- ret = -EINTR;
- goto err_unreserve;
- }
- i915_retire_requests(i915);
+ if (rq)
+ cond_synchronize_rcu(rq->rcustate);
/*
* We've forced the client to stall and catch up with whatever
@@ -762,6 +758,8 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx)
}
}
+ rq->rcustate = get_state_synchronize_rcu();
+
INIT_LIST_HEAD(&rq->active_list);
rq->i915 = i915;
rq->engine = engine;
diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
index 9898301ab7ef..7fa94b024968 100644
--- a/drivers/gpu/drm/i915/i915_request.h
+++ b/drivers/gpu/drm/i915/i915_request.h
@@ -100,6 +100,14 @@ struct i915_request {
struct i915_timeline *timeline;
struct intel_signal_node signaling;
+ /*
+ * The rcu epoch of when this request was allocated. Used to judiciously
+ * apply backpressure on future allocations to ensure that under
+ * mempressure there is sufficient RCU ticks for us to reclaim our
+ * RCU protected slabs.
+ */
+ unsigned long rcustate;
+
/*
* Fences for the various phases in the request's lifetime.
*
--
2.19.0
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