linux-kernel - [PATCH] drm/vc4: Fulfill user BO creation requests from the kernel BO cache.

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Message-Id: <20170209005238.28326-1-eric@anholt.net>
Date:   Wed,  8 Feb 2017 16:52:38 -0800
From:   Eric Anholt <eric@...olt.net>
To:     dri-devel@...ts.freedesktop.org
Cc:     linux-kernel@...r.kernel.org, Eric Anholt <eric@...olt.net>
Subject: [PATCH] drm/vc4: Fulfill user BO creation requests from the kernel BO cache.

The from_cache flag was actually "the BO is invisible to userspace",
so we can repurpose to just zero out a cached BO and return it to
userspace.

Improves wall time for a loop of 5 glsl-algebraic-add-add-1 by
-1.44989% +/- 0.862891% (n=28, 1 outlier removed from each that
appeared to be other system noise)

Note that there's an intel-gpu-tools test to check for the proper
zeroing behavior here, which we continue to pass.

Signed-off-by: Eric Anholt <eric@...olt.net>
---
 drivers/gpu/drm/vc4/vc4_bo.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_bo.c b/drivers/gpu/drm/vc4/vc4_bo.c
index 3f6704cf6608..5ec14f25625d 100644
--- a/drivers/gpu/drm/vc4/vc4_bo.c
+++ b/drivers/gpu/drm/vc4/vc4_bo.c
@@ -208,21 +208,22 @@ struct drm_gem_object *vc4_create_object(struct drm_device *dev, size_t size)
 }

 struct vc4_bo *vc4_bo_create(struct drm_device *dev, size_t unaligned_size,
-			     bool from_cache)
+			     bool allow_unzeroed)
 {
 	size_t size = roundup(unaligned_size, PAGE_SIZE);
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	struct drm_gem_cma_object *cma_obj;
+	struct vc4_bo *bo;

 	if (size == 0)
 		return ERR_PTR(-EINVAL);

 	/* First, try to get a vc4_bo from the kernel BO cache. */
-	if (from_cache) {
-		struct vc4_bo *bo = vc4_bo_get_from_cache(dev, size);
-
-		if (bo)
-			return bo;
+	bo = vc4_bo_get_from_cache(dev, size);
+	if (bo) {
+		if (!allow_unzeroed)
+			memset(bo->base.vaddr, 0, bo->base.base.size);
+		return bo;
 	}

 	cma_obj = drm_gem_cma_create(dev, size);
-- 
2.11.0