NO_EVICT bos that are not idle when all references are dropped are put on the delayed destroy list. However, since they are not on LRU lists, they are not available to shrinkers at that point, and buffers on the delayed destroy list are not checked very often for idle.

So when these buffers are put on the delayed destroy list, clear the NO_EVICT flag and put them on the right LRU list. This way they are immediately available for eviction or shrinkers and will not cause false OOMS.

Signed-off-by: Thomas Hellstrom thellstrom@vmware.com --- drivers/gpu/drm/ttm/ttm_bo.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index f1a857e..6c1a38f 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -429,8 +429,20 @@ static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo) sync_obj = driver->sync_obj_ref(bo->sync_obj); spin_unlock(&bdev->fence_lock);

- if (!ret) + if (!ret) { + + /* + * Make NO_EVICT bos immediately available to + * shrinkers, now that they are queued for + * destruction. + */ + if (bo->mem.placement & TTM_PL_FLAG_NO_EVICT) { + bo->mem.placement &= ~TTM_PL_FLAG_NO_EVICT; + ttm_bo_add_to_lru(bo); + } + ww_mutex_unlock(&bo->resv->lock); + }

kref_get(&bo->list_kref); list_add_tail(&bo->ddestroy, &bdev->ddestroy);

On Thu, Oct 10, 2013 at 8:22 PM, Thomas Hellstrom thellstrom@vmware.com wrote:

Make use of the FAULT_FLAG_ALLOW_RETRY flag to allow dropping the mmap_sem while waiting for bo idle.

FAULT_FLAG_ALLOW_RETRY appears to be primarily designed for disk waits but should work just as fine for GPU waits..

Signed-off-by: Thomas Hellstrom thellstrom@vmware.com

Reviewed-by: Jakob Bornecrantz jakob@vmware.com

Tho somebody else should also take a look at this.

---

drivers/gpu/drm/ttm/ttm_bo_vm.c | 62 +++++++++++++++++++++++++++++++-------- 1 file changed, 50 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c index 1006c15..c03514b 100644 --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c @@ -41,6 +41,51 @@

#define TTM_BO_VM_NUM_PREFAULT 16

+static int ttm_bo_vm_fault_idle(struct ttm_buffer_object *bo,

•                           struct vm_area_struct *vma,
  

•                           struct vm_fault *vmf)
  

+{

•   struct ttm_bo_device *bdev = bo->bdev;
  

•   int ret = 0;
  

•   spin_lock(&bdev->fence_lock);
  

•   if (likely(!test_bit(TTM_BO_PRIV_FLAG_MOVING, &bo->priv_flags)))
  

•           goto out_unlock;
  

•   /*
  

•    * Quick non-stalling check for idle.
  

•    */
  

•   ret = ttm_bo_wait(bo, false, false, true);
  

•   if (likely(ret == 0))
  

•           goto out_unlock;
  

•   /*
  

•    * If possible, avoid waiting for GPU with mmap_sem
  

•    * held.
  

•    */
  

•   if (vmf->flags & FAULT_FLAG_ALLOW_RETRY) {
  

•           ret = VM_FAULT_RETRY;
  

•           if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
  

•                   goto out_unlock;
  

•           up_read(&vma->vm_mm->mmap_sem);
  

•           (void) ttm_bo_wait(bo, false, true, false);
  

•           goto out_unlock;
  

•   }
  

•   /*
  

•    * Ordinary wait.
  

•    */
  

•   ret = ttm_bo_wait(bo, false, true, false);
  

•   if (unlikely(ret != 0))
  

•           ret = (ret != -ERESTARTSYS) ? VM_FAULT_SIGBUS :
  

•                   VM_FAULT_NOPAGE;
  

+out_unlock:

•   spin_unlock(&bdev->fence_lock);
  

•   return ret;
  

+}

static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf) { struct ttm_buffer_object *bo = (struct ttm_buffer_object *) @@ -91,18 +136,11 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf) * Wait for buffer data in transit, due to a pipelined * move. */

•   spin_lock(&bdev->fence_lock);
  

•   if (test_bit(TTM_BO_PRIV_FLAG_MOVING, &bo->priv_flags)) {
  

•           ret = ttm_bo_wait(bo, false, true, false);
  

•           spin_unlock(&bdev->fence_lock);
  

•           if (unlikely(ret != 0)) {
  

•                   retval = (ret != -ERESTARTSYS) ?
  

•                       VM_FAULT_SIGBUS : VM_FAULT_NOPAGE;
  

•                   goto out_unlock;
  

•           }
  

•   } else
  

•           spin_unlock(&bdev->fence_lock);
  

•   ret = ttm_bo_vm_fault_idle(bo, vma, vmf);
  

•   if (unlikely(ret != 0)) {
  

•           retval = ret;
  

•           goto out_unlock;
  

•   }
  
    ret = ttm_mem_io_lock(man, true);
    if (unlikely(ret != 0)) {
  

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