On Thu, Apr 1, 2021 at 8:34 AM Doug Anderson dianders@chromium.org wrote:

Hi,

On Wed, Mar 31, 2021 at 6:24 PM Rob Clark robdclark@gmail.com wrote:

...

@@ -45,6 +30,9 @@ msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc) list_for_each_entry(msm_obj, &priv->inactive_dontneed, mm_list) { if (freed >= sc->nr_to_scan) break;

•           /* Use trylock, because we cannot block on a obj that
  

•            * might be trying to acquire mm_lock
  

•            */
  

nit: I thought the above multi-line commenting style was only for "net" subsystem?

we do use the "net" style a fair bit already.. (OTOH I tend to not really care what checkpatch says)

...

            if (!msm_gem_trylock(&msm_obj->base))
                    continue;
            if (is_purgeable(msm_obj)) {

@@ -56,8 +44,11 @@ msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)

    mutex_unlock(&priv->mm_lock);

•   if (freed > 0)
  

•   if (freed > 0) {
            trace_msm_gem_purge(freed << PAGE_SHIFT);
  

•   } else {
  

•           return SHRINK_STOP;
  

•   }
  

It probably doesn't matter, but I wonder if we should still be returning SHRINK_STOP if we got any trylock failures. It could possibly be worth returning 0 in that case?

On the surface, you'd think that, but there be mm dragons.. we can hit shrinker from the submit path when the obj is locked already and we are trying to allocate backing pages. We don't want to tell vmscan to keep trying, because we'll keep failing to grab that objects lock

...

@@ -75,6 +66,9 @@ vmap_shrink(struct list_head *mm_list) unsigned unmapped = 0;

    list_for_each_entry(msm_obj, mm_list, mm_list) {

•           /* Use trylock, because we cannot block on a obj that
  

•            * might be trying to acquire mm_lock
  

•            */
  

If you end up changing the commenting style above, should also be here.

At this point this seems fine to land to me. Though I'm not an expert on every interaction in this code, I've spent enough time starting at it that I'm comfortable with:

Reviewed-by: Douglas Anderson dianders@chromium.org

thanks

BR, -R