This is a note to let you know that I've just added the patch titled
drm/nouveau: wait for the exclusive fence after the shared ones v2
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-nouveau-wait-for-the-exclusive-fence-after-the-shared-ones-v2.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 67f74302f45d5d862f22ced3297624e50ac352f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@xxxxxxx>
Date: Tue, 7 Dec 2021 10:10:15 +0100
Subject: drm/nouveau: wait for the exclusive fence after the shared ones v2
MIME-Version: 1.0
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From: Christian König <christian.koenig@xxxxxxx>
commit 67f74302f45d5d862f22ced3297624e50ac352f0 upstream.
Always waiting for the exclusive fence resulted on some performance
regressions. So try to wait for the shared fences first, then the
exclusive fence should always be signaled already.
v2: fix incorrectly placed "(", add some comment why we do this.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
Tested-by: Stefan Fritsch <sf@xxxxxxxxxxx>
Tested-by: Dan Moulding <dmoulding@xxxxxx>
Acked-by: Ben Skeggs <bskeggs@xxxxxxxxxx>
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20211209102335.18321-1-christian.koenig@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/nouveau/nouveau_fence.c | 28 +++++++++++++++-------------
1 file changed, 15 insertions(+), 13 deletions(-)
--- a/drivers/gpu/drm/nouveau/nouveau_fence.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
@@ -353,15 +353,22 @@ nouveau_fence_sync(struct nouveau_bo *nv
if (ret)
return ret;
- }
- fobj = dma_resv_shared_list(resv);
- fence = dma_resv_excl_fence(resv);
+ fobj = NULL;
+ } else {
+ fobj = dma_resv_shared_list(resv);
+ }
- if (fence) {
+ /* Waiting for the exclusive fence first causes performance regressions
+ * under some circumstances. So manually wait for the shared ones first.
+ */
+ for (i = 0; i < (fobj ? fobj->shared_count : 0) && !ret; ++i) {
struct nouveau_channel *prev = NULL;
bool must_wait = true;
+ fence = rcu_dereference_protected(fobj->shared[i],
+ dma_resv_held(resv));
+
f = nouveau_local_fence(fence, chan->drm);
if (f) {
rcu_read_lock();
@@ -373,20 +380,13 @@ nouveau_fence_sync(struct nouveau_bo *nv
if (must_wait)
ret = dma_fence_wait(fence, intr);
-
- return ret;
}
- if (!exclusive || !fobj)
- return ret;
-
- for (i = 0; i < fobj->shared_count && !ret; ++i) {
+ fence = dma_resv_excl_fence(resv);
+ if (fence) {
struct nouveau_channel *prev = NULL;
bool must_wait = true;
- fence = rcu_dereference_protected(fobj->shared[i],
- dma_resv_held(resv));
-
f = nouveau_local_fence(fence, chan->drm);
if (f) {
rcu_read_lock();
@@ -398,6 +398,8 @@ nouveau_fence_sync(struct nouveau_bo *nv
if (must_wait)
ret = dma_fence_wait(fence, intr);
+
+ return ret;
}
return ret;
Patches currently in stable-queue which might be from christian.koenig@xxxxxxx are
queue-5.15/drm-nouveau-wait-for-the-exclusive-fence-after-the-shared-ones-v2.patch
