On Thu, Apr 1, 2021 at 8:34 AM Doug Anderson <dianders(a)chromium.org> wrote:
>
> Hi,
>
> On Wed, Mar 31, 2021 at 6:24 PM Rob Clark <robdclark(a)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(a)chromium.org>
thanks
BR,
-R
From: Rob Clark <robdclark(a)chromium.org>
I've been spending some time looking into how things behave under high
memory pressure. The first patch is a random cleanup I noticed along
the way. The second improves the situation significantly when we are
getting shrinker called from many threads in parallel. And the last
two are $debugfs/gem fixes I needed so I could monitor the state of GEM
objects (ie. how many are active/purgable/purged) while triggering high
memory pressure.
We could probably go a bit further with dropping the mm_lock in the
shrinker->scan() loop, but this is already a pretty big improvement.
The next step is probably actually to add support to unpin/evict
inactive objects. (We are part way there since we have already de-
coupled the iova lifetime from the pages lifetime, but there are a
few sharp corners to work through.)
Rob Clark (4):
drm/msm: Remove unused freed llist node
drm/msm: Avoid mutex in shrinker_count()
drm/msm: Fix debugfs deadlock
drm/msm: Improved debugfs gem stats
drivers/gpu/drm/msm/msm_debugfs.c | 14 ++---
drivers/gpu/drm/msm/msm_drv.c | 4 ++
drivers/gpu/drm/msm/msm_drv.h | 15 ++++--
drivers/gpu/drm/msm/msm_fb.c | 3 +-
drivers/gpu/drm/msm/msm_gem.c | 65 ++++++++++++++++++-----
drivers/gpu/drm/msm/msm_gem.h | 72 +++++++++++++++++++++++---
drivers/gpu/drm/msm/msm_gem_shrinker.c | 28 ++++------
7 files changed, 150 insertions(+), 51 deletions(-)
--
2.30.2
