From: Rob Clark robdclark@chromium.org
lock_stat + mmm_donut[1] say that this reduces contention on mm_lock significantly (~350x lower waittime-max, and ~100x lower waittime-avg)
[1] https://chromium.googlesource.com/chromiumos/platform/microbenchmarks/+/refs...
Signed-off-by: Rob Clark robdclark@chromium.org --- drivers/gpu/drm/msm/msm_gem.c | 2 +- drivers/gpu/drm/msm/msm_gem_shrinker.c | 48 ++++++++++++++++++++++---- 2 files changed, 43 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c index 2ecf7f1cef25..75cea5b801da 100644 --- a/drivers/gpu/drm/msm/msm_gem.c +++ b/drivers/gpu/drm/msm/msm_gem.c @@ -719,7 +719,7 @@ void msm_gem_purge(struct drm_gem_object *obj) put_iova_vmas(obj);
msm_obj->madv = __MSM_MADV_PURGED; - mark_unpurgable(msm_obj); + update_inactive(msm_obj);
drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping); drm_gem_free_mmap_offset(obj); diff --git a/drivers/gpu/drm/msm/msm_gem_shrinker.c b/drivers/gpu/drm/msm/msm_gem_shrinker.c index f3e948af01c5..6bbb15d64861 100644 --- a/drivers/gpu/drm/msm/msm_gem_shrinker.c +++ b/drivers/gpu/drm/msm/msm_gem_shrinker.c @@ -22,26 +22,62 @@ msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc) { struct msm_drm_private *priv = container_of(shrinker, struct msm_drm_private, shrinker); - struct msm_gem_object *msm_obj; + struct list_head still_in_list; unsigned long freed = 0;
+ INIT_LIST_HEAD(&still_in_list); + mutex_lock(&priv->mm_lock);
- list_for_each_entry(msm_obj, &priv->inactive_dontneed, mm_list) { - if (freed >= sc->nr_to_scan) + while (freed < sc->nr_to_scan) { + struct msm_gem_object *msm_obj = list_first_entry_or_null( + &priv->inactive_dontneed, typeof(*msm_obj), mm_list); + + if (!msm_obj) break; - /* Use trylock, because we cannot block on a obj that - * might be trying to acquire mm_lock + + /* + * If it is in the process of being freed, msm_gem_free_object + * can be blocked on mm_lock waiting to remove it. So just + * skip it. */ - if (!msm_gem_trylock(&msm_obj->base)) + if (!kref_get_unless_zero(&msm_obj->base.refcount)) continue; + + /* + * Now that we own a reference, we can move it to our own + * private temporary list and drop mm_lock for the rest of + * the loop body, to reduce contention with the retire_submit + * path (which could make more objects available to purge) + */ + list_move_tail(&msm_obj->mm_list, &still_in_list); + + mutex_unlock(&priv->mm_lock); + + /* + * Note that this still needs to be trylock, since we can + * hit shrinker in response to trying to get backing pages + * for this obj (ie. while it's lock is already held) + */ + if (!msm_gem_trylock(&msm_obj->base)) + goto tail; + if (is_purgeable(msm_obj)) { + /* + * This will move the obj out of still_in_list to + * the purged list + */ msm_gem_purge(&msm_obj->base); freed += msm_obj->base.size >> PAGE_SHIFT; } msm_gem_unlock(&msm_obj->base); + +tail: + drm_gem_object_put(&msm_obj->base); + mutex_lock(&priv->mm_lock); }
+ list_splice_tail(&still_in_list, &priv->inactive_dontneed); mutex_unlock(&priv->mm_lock);
if (freed > 0) {