From d7d82f5d5c04ed9cb68d3663ffde10898a2969be Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Wed, 23 Dec 2020 12:20:50 +0000 Subject: [PATCH] drm/i915/gt: Prefer recycling an idle fence If we want to reuse a fence that is in active use by the GPU, we have to wait an uncertain amount of time, but if we reuse an inactive fence, we can change it right away. Loop through the list of available fences twice, ignoring any active fences on the first pass. Signed-off-by: Chris Wilson Reviewed-by: Mika Kuoppala Link: https://patchwork.freedesktop.org/patch/msgid/20201223122051.4624-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c | 22 ++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c b/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c index 7fb36b12fe7a..a357bb431815 100644 --- a/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c +++ b/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c @@ -320,13 +320,31 @@ void i915_vma_revoke_fence(struct i915_vma *vma) fence_write(fence); } +static bool fence_is_active(const struct i915_fence_reg *fence) +{ + return fence->vma && i915_vma_is_active(fence->vma); +} + static struct i915_fence_reg *fence_find(struct i915_ggtt *ggtt) { - struct i915_fence_reg *fence; + struct i915_fence_reg *active = NULL; + struct i915_fence_reg *fence, *fn; - list_for_each_entry(fence, &ggtt->fence_list, link) { + list_for_each_entry_safe(fence, fn, &ggtt->fence_list, link) { GEM_BUG_ON(fence->vma && fence->vma->fence != fence); + if (fence == active) /* now seen this fence twice */ + active = ERR_PTR(-EAGAIN); + + /* Prefer idle fences so we do not have to wait on the GPU */ + if (active != ERR_PTR(-EAGAIN) && fence_is_active(fence)) { + if (!active) + active = fence; + + list_move_tail(&fence->link, &ggtt->fence_list); + continue; + } + if (atomic_read(&fence->pin_count)) continue;