diff mbox series

drm/ttm: Remove pinned bos from LRU in ttm_bo_move_to_lru_tail()

Message ID 20210104231358.154521-1-lyude@redhat.com (mailing list archive)
State New, archived
Headers show
Series drm/ttm: Remove pinned bos from LRU in ttm_bo_move_to_lru_tail() | expand

Commit Message

Lyude Paul Jan. 4, 2021, 11:13 p.m. UTC
Recently a regression was introduced which caused TTM's buffer eviction to
attempt to evict already-pinned BOs, causing issues with buffer eviction
under memory pressure along with suspend/resume:

  nouveau 0000:1f:00.0: DRM: evicting buffers...
  nouveau 0000:1f:00.0: DRM: Moving pinned object 00000000c428c3ff!
  nouveau 0000:1f:00.0: fifo: fault 00 [READ] at 0000000000200000 engine 04
  [BAR1] client 07 [HUB/HOST_CPU] reason 02 [PTE] on channel -1 [00ffeaa000
  unknown]
  nouveau 0000:1f:00.0: fifo: DROPPED_MMU_FAULT 00001000
  nouveau 0000:1f:00.0: fifo: fault 01 [WRITE] at 0000000000020000 engine
  0c [HOST6] client 07 [HUB/HOST_CPU] reason 02 [PTE] on channel 1
  [00ffb28000 DRM]
  nouveau 0000:1f:00.0: fifo: channel 1: killed
  nouveau 0000:1f:00.0: fifo: runlist 0: scheduled for recovery
  [TTM] Buffer eviction failed
  nouveau 0000:1f:00.0: DRM: waiting for kernel channels to go idle...
  nouveau 0000:1f:00.0: DRM: failed to idle channel 1 [DRM]
  nouveau 0000:1f:00.0: DRM: resuming display...

After some bisection and investigation, it appears this resulted from the
recent changes to ttm_bo_move_to_lru_tail(). Previously when a buffer was
pinned, the buffer would be removed from the LRU once ttm_bo_unreserve
to maintain the LRU list when pinning or unpinning BOs. However, since:

commit 3d1a88e1051f ("drm/ttm: cleanup LRU handling further")

We've been exiting from ttm_bo_move_to_lru_tail() at the very beginning of
the function if the bo we're looking at is pinned, resulting in the pinned
BO never getting removed from the lru and as a result - causing issues when
it eventually becomes time for eviction.

So, let's fix this by calling ttm_bo_del_from_lru() from
ttm_bo_move_to_lru_tail() in the event that we're dealing with a pinned
buffer. As well, add back the hunks in ttm_bo_del_from_lru() that were
removed which checked whether we want to call
bdev->driver->del_from_lru_notify() or not. We do this last part to avoid
calling the hook when the bo in question was already removed from the LRU.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Fixes: 3d1a88e1051f ("drm/ttm: cleanup LRU handling further")
Cc: Christian König <christian.koenig@amd.com>
Cc: Dave Airlie <airlied@redhat.com>
---
 drivers/gpu/drm/ttm/ttm_bo.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

Comments

Christian König Jan. 4, 2021, 9:06 p.m. UTC | #1
Am 05.01.21 um 00:13 schrieb Lyude Paul:
> Recently a regression was introduced which caused TTM's buffer eviction to
> attempt to evict already-pinned BOs, causing issues with buffer eviction
> under memory pressure along with suspend/resume:
>
>    nouveau 0000:1f:00.0: DRM: evicting buffers...
>    nouveau 0000:1f:00.0: DRM: Moving pinned object 00000000c428c3ff!
>    nouveau 0000:1f:00.0: fifo: fault 00 [READ] at 0000000000200000 engine 04
>    [BAR1] client 07 [HUB/HOST_CPU] reason 02 [PTE] on channel -1 [00ffeaa000
>    unknown]
>    nouveau 0000:1f:00.0: fifo: DROPPED_MMU_FAULT 00001000
>    nouveau 0000:1f:00.0: fifo: fault 01 [WRITE] at 0000000000020000 engine
>    0c [HOST6] client 07 [HUB/HOST_CPU] reason 02 [PTE] on channel 1
>    [00ffb28000 DRM]
>    nouveau 0000:1f:00.0: fifo: channel 1: killed
>    nouveau 0000:1f:00.0: fifo: runlist 0: scheduled for recovery
>    [TTM] Buffer eviction failed
>    nouveau 0000:1f:00.0: DRM: waiting for kernel channels to go idle...
>    nouveau 0000:1f:00.0: DRM: failed to idle channel 1 [DRM]
>    nouveau 0000:1f:00.0: DRM: resuming display...
>
> After some bisection and investigation, it appears this resulted from the
> recent changes to ttm_bo_move_to_lru_tail(). Previously when a buffer was
> pinned, the buffer would be removed from the LRU once ttm_bo_unreserve
> to maintain the LRU list when pinning or unpinning BOs. However, since:
>
> commit 3d1a88e1051f ("drm/ttm: cleanup LRU handling further")
>
> We've been exiting from ttm_bo_move_to_lru_tail() at the very beginning of
> the function if the bo we're looking at is pinned, resulting in the pinned
> BO never getting removed from the lru and as a result - causing issues when
> it eventually becomes time for eviction.
>
> So, let's fix this by calling ttm_bo_del_from_lru() from
> ttm_bo_move_to_lru_tail() in the event that we're dealing with a pinned
> buffer. As well, add back the hunks in ttm_bo_del_from_lru() that were
> removed which checked whether we want to call
> bdev->driver->del_from_lru_notify() or not. We do this last part to avoid
> calling the hook when the bo in question was already removed from the LRU.
>
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Fixes: 3d1a88e1051f ("drm/ttm: cleanup LRU handling further")
> Cc: Christian König <christian.koenig@amd.com>
> Cc: Dave Airlie <airlied@redhat.com>

I was already working on a fix as well, but you have been faster than me :)

Reviewed-by: Christian König <christian.koenig@amd.com>

Going to pick this up for drm-misc-next or drm-misc-fixes in a few minutes.

Thanks,
Christian.

> ---
>   drivers/gpu/drm/ttm/ttm_bo.c | 20 ++++++++++++++++----
>   1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index 31e8b3da5563..0f373b78e7fa 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -113,11 +113,18 @@ static struct kobj_type ttm_bo_glob_kobj_type  = {
>   static void ttm_bo_del_from_lru(struct ttm_buffer_object *bo)
>   {
>   	struct ttm_bo_device *bdev = bo->bdev;
> +	bool notify = false;
>   
> -	list_del_init(&bo->swap);
> -	list_del_init(&bo->lru);
> +	if (!list_empty(&bo->swap)) {
> +		notify = true;
> +		list_del_init(&bo->swap);
> +	}
> +	if (!list_empty(&bo->lru)) {
> +		notify = true;
> +		list_del_init(&bo->lru);
> +	}
>   
> -	if (bdev->driver->del_from_lru_notify)
> +	if (notify && bdev->driver->del_from_lru_notify)
>   		bdev->driver->del_from_lru_notify(bo);
>   }
>   
> @@ -138,8 +145,13 @@ void ttm_bo_move_to_lru_tail(struct ttm_buffer_object *bo,
>   
>   	dma_resv_assert_held(bo->base.resv);
>   
> -	if (bo->pin_count)
> +	/* Pinned bos will have been added to the LRU before they were pinned, so make sure we
> +	 * always remove them here
> +	 */
> +	if (bo->pin_count) {
> +		ttm_bo_del_from_lru(bo);
>   		return;
> +	}
>   
>   	man = ttm_manager_type(bdev, mem->mem_type);
>   	list_move_tail(&bo->lru, &man->lru[bo->priority]);
Christian König Jan. 5, 2021, 11:49 a.m. UTC | #2
Am 04.01.21 um 22:06 schrieb Christian König:
> Am 05.01.21 um 00:13 schrieb Lyude Paul:
>> Recently a regression was introduced which caused TTM's buffer 
>> eviction to
>> attempt to evict already-pinned BOs, causing issues with buffer eviction
>> under memory pressure along with suspend/resume:
>>
>>    nouveau 0000:1f:00.0: DRM: evicting buffers...
>>    nouveau 0000:1f:00.0: DRM: Moving pinned object 00000000c428c3ff!
>>    nouveau 0000:1f:00.0: fifo: fault 00 [READ] at 0000000000200000 
>> engine 04
>>    [BAR1] client 07 [HUB/HOST_CPU] reason 02 [PTE] on channel -1 
>> [00ffeaa000
>>    unknown]
>>    nouveau 0000:1f:00.0: fifo: DROPPED_MMU_FAULT 00001000
>>    nouveau 0000:1f:00.0: fifo: fault 01 [WRITE] at 0000000000020000 
>> engine
>>    0c [HOST6] client 07 [HUB/HOST_CPU] reason 02 [PTE] on channel 1
>>    [00ffb28000 DRM]
>>    nouveau 0000:1f:00.0: fifo: channel 1: killed
>>    nouveau 0000:1f:00.0: fifo: runlist 0: scheduled for recovery
>>    [TTM] Buffer eviction failed
>>    nouveau 0000:1f:00.0: DRM: waiting for kernel channels to go idle...
>>    nouveau 0000:1f:00.0: DRM: failed to idle channel 1 [DRM]
>>    nouveau 0000:1f:00.0: DRM: resuming display...
>>
>> After some bisection and investigation, it appears this resulted from 
>> the
>> recent changes to ttm_bo_move_to_lru_tail(). Previously when a buffer 
>> was
>> pinned, the buffer would be removed from the LRU once ttm_bo_unreserve
>> to maintain the LRU list when pinning or unpinning BOs. However, since:
>>
>> commit 3d1a88e1051f ("drm/ttm: cleanup LRU handling further")
>>
>> We've been exiting from ttm_bo_move_to_lru_tail() at the very 
>> beginning of
>> the function if the bo we're looking at is pinned, resulting in the 
>> pinned
>> BO never getting removed from the lru and as a result - causing 
>> issues when
>> it eventually becomes time for eviction.
>>
>> So, let's fix this by calling ttm_bo_del_from_lru() from
>> ttm_bo_move_to_lru_tail() in the event that we're dealing with a pinned
>> buffer.

>> As well, add back the hunks in ttm_bo_del_from_lru() that were
>> removed which checked whether we want to call
>> bdev->driver->del_from_lru_notify() or not. We do this last part to 
>> avoid
>> calling the hook when the bo in question was already removed from the 
>> LRU.

It turned out that this is not correct, we always want to call the 
callback whenever we would move the BO on the LRU.

I've modified the patch and send it out once more, please review.

Thanks,
Christian.

>>
>> Signed-off-by: Lyude Paul <lyude@redhat.com>
>> Fixes: 3d1a88e1051f ("drm/ttm: cleanup LRU handling further")
>> Cc: Christian König <christian.koenig@amd.com>
>> Cc: Dave Airlie <airlied@redhat.com>
>
> I was already working on a fix as well, but you have been faster than 
> me :)
>
> Reviewed-by: Christian König <christian.koenig@amd.com>
>
> Going to pick this up for drm-misc-next or drm-misc-fixes in a few 
> minutes.
>
> Thanks,
> Christian.
>
>> ---
>>   drivers/gpu/drm/ttm/ttm_bo.c | 20 ++++++++++++++++----
>>   1 file changed, 16 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>> index 31e8b3da5563..0f373b78e7fa 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>> @@ -113,11 +113,18 @@ static struct kobj_type ttm_bo_glob_kobj_type  = {
>>   static void ttm_bo_del_from_lru(struct ttm_buffer_object *bo)
>>   {
>>       struct ttm_bo_device *bdev = bo->bdev;
>> +    bool notify = false;
>>   -    list_del_init(&bo->swap);
>> -    list_del_init(&bo->lru);
>> +    if (!list_empty(&bo->swap)) {
>> +        notify = true;
>> +        list_del_init(&bo->swap);
>> +    }
>> +    if (!list_empty(&bo->lru)) {
>> +        notify = true;
>> +        list_del_init(&bo->lru);
>> +    }
>>   -    if (bdev->driver->del_from_lru_notify)
>> +    if (notify && bdev->driver->del_from_lru_notify)
>>           bdev->driver->del_from_lru_notify(bo);
>>   }
>>   @@ -138,8 +145,13 @@ void ttm_bo_move_to_lru_tail(struct 
>> ttm_buffer_object *bo,
>>         dma_resv_assert_held(bo->base.resv);
>>   -    if (bo->pin_count)
>> +    /* Pinned bos will have been added to the LRU before they were 
>> pinned, so make sure we
>> +     * always remove them here
>> +     */
>> +    if (bo->pin_count) {
>> +        ttm_bo_del_from_lru(bo);
>>           return;
>> +    }
>>         man = ttm_manager_type(bdev, mem->mem_type);
>>       list_move_tail(&bo->lru, &man->lru[bo->priority]);
>
diff mbox series

Patch

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 31e8b3da5563..0f373b78e7fa 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -113,11 +113,18 @@  static struct kobj_type ttm_bo_glob_kobj_type  = {
 static void ttm_bo_del_from_lru(struct ttm_buffer_object *bo)
 {
 	struct ttm_bo_device *bdev = bo->bdev;
+	bool notify = false;
 
-	list_del_init(&bo->swap);
-	list_del_init(&bo->lru);
+	if (!list_empty(&bo->swap)) {
+		notify = true;
+		list_del_init(&bo->swap);
+	}
+	if (!list_empty(&bo->lru)) {
+		notify = true;
+		list_del_init(&bo->lru);
+	}
 
-	if (bdev->driver->del_from_lru_notify)
+	if (notify && bdev->driver->del_from_lru_notify)
 		bdev->driver->del_from_lru_notify(bo);
 }
 
@@ -138,8 +145,13 @@  void ttm_bo_move_to_lru_tail(struct ttm_buffer_object *bo,
 
 	dma_resv_assert_held(bo->base.resv);
 
-	if (bo->pin_count)
+	/* Pinned bos will have been added to the LRU before they were pinned, so make sure we
+	 * always remove them here
+	 */
+	if (bo->pin_count) {
+		ttm_bo_del_from_lru(bo);
 		return;
+	}
 
 	man = ttm_manager_type(bdev, mem->mem_type);
 	list_move_tail(&bo->lru, &man->lru[bo->priority]);