On 16/01/2018 13:15, Chris Wilson wrote:
If we fail to allocate a new request, make sure we recover the pages
that are in the process of being freed by inserting an RCU barrier.
v2: Comment before the shrink and barrier in the error path.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_request.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 72bdc203716f..a0f451b4a4e8 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -696,6 +696,17 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
if (ret)
goto err_unreserve;
+ /*
+ * 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(dev_priv->requests);
+ rcu_barrier(); /* Recover the TYPESAFE_BY_RCU pages */
+
req = kmem_cache_alloc(dev_priv->requests, GFP_KERNEL);
if (!req) {
ret = -ENOMEM;
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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