From cb0aeaa81842948e32f39838f0ec113e3bb52291 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Wed, 5 Jul 2017 15:26:34 +0100 Subject: [PATCH] drm/i915: Only free the oldest stale context before allocating Currently, we move all unreferenced contexts to an RCU free list and then onto a worker for eventual reaping. To compensate against this growing into a long list with frequent allocations starving the system of available memory, before we allocate a new context we reap all the stale contexts. This puts all the cost of destroying the context into the next allocator, which is presumably more sensitive to syscall latency and unfair. We can limit the number of contexts being freed by the new allocator to both keep the list trimmed and to allow the allocator to be reasonably fast. Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Link: http://patchwork.freedesktop.org/patch/msgid/20170705142634.18554-4-chris@chris-wilson.co.uk Reviewed-by: Tvrtko Ursulin --- drivers/gpu/drm/i915/i915_gem_context.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c index 4f6773ea7d85..1a87d04e7937 100644 --- a/drivers/gpu/drm/i915/i915_gem_context.c +++ b/drivers/gpu/drm/i915/i915_gem_context.c @@ -201,6 +201,21 @@ static void contexts_free(struct drm_i915_private *i915) i915_gem_context_free(ctx); } +static void contexts_free_first(struct drm_i915_private *i915) +{ + struct i915_gem_context *ctx; + struct llist_node *freed; + + lockdep_assert_held(&i915->drm.struct_mutex); + + freed = llist_del_first(&i915->contexts.free_list); + if (!freed) + return; + + ctx = container_of(freed, typeof(*ctx), free_link); + i915_gem_context_free(ctx); +} + static void contexts_free_worker(struct work_struct *work) { struct drm_i915_private *i915 = @@ -383,8 +398,8 @@ i915_gem_create_context(struct drm_i915_private *dev_priv, lockdep_assert_held(&dev_priv->drm.struct_mutex); - /* Reap stale contexts */ - contexts_free(dev_priv); + /* Reap the most stale context */ + contexts_free_first(dev_priv); ctx = __create_hw_context(dev_priv, file_priv); if (IS_ERR(ctx)) -- 2.30.2