On 28.01.2021 02:33, Yang Shi wrote:
> Use per memcg's nr_deferred for memcg aware shrinkers. The shrinker's nr_deferred
> will be used in the following cases:
> 1. Non memcg aware shrinkers
> 2. !CONFIG_MEMCG
> 3. memcg is disabled by boot parameter
>
> Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
> ---
> mm/vmscan.c | 87 ++++++++++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 73 insertions(+), 14 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 20be0db291fe..e1f8960f5cf6 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -205,7 +205,8 @@ static int expand_one_shrinker_info(struct mem_cgroup *memcg,
>
> for_each_node(nid) {
> old = rcu_dereference_protected(
> - mem_cgroup_nodeinfo(memcg, nid)->shrinker_info, true);
> + mem_cgroup_nodeinfo(memcg, nid)->shrinker_info,
> + lockdep_is_held(&shrinker_rwsem));
Won't it better to pack this repeating pattern into helper function, e.g.:
static struct shrinker_info memcg_shrinker_info(struct mem_cgroup *memcg, int nid)
{
return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
lockdep_is_held(&shrinker_rwsem));
}
?
Even shrink_slab_memcg() may want to use it.
> /* Not yet online memcg */
> if (!old)
> return 0;
> @@ -239,7 +240,8 @@ void free_shrinker_info(struct mem_cgroup *memcg)
>
> for_each_node(nid) {
> pn = mem_cgroup_nodeinfo(memcg, nid);
> - info = rcu_dereference_protected(pn->shrinker_info, true);
> + info = rcu_dereference_protected(pn->shrinker_info,
> + lockdep_is_held(&shrinker_rwsem));
> if (info)
> kvfree(info);
> rcu_assign_pointer(pn->shrinker_info, NULL);
> @@ -360,6 +362,27 @@ static void unregister_memcg_shrinker(struct shrinker *shrinker)
> up_write(&shrinker_rwsem);
> }
>
> +static long count_nr_deferred_memcg(int nid, struct shrinker *shrinker,
> + struct mem_cgroup *memcg)
> +{
> + struct shrinker_info *info;
> +
> + info = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
> + lockdep_is_held(&shrinker_rwsem));
> + return atomic_long_xchg(&info->nr_deferred[shrinker->id], 0);
> +}
> +
> +static long set_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
> + struct mem_cgroup *memcg)
> +{
> + struct shrinker_info *info;
> +
> + info = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
> + lockdep_is_held(&shrinker_rwsem));
> +
> + return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]);
> +}
> +
> static bool cgroup_reclaim(struct scan_control *sc)
> {
> return sc->target_mem_cgroup;
> @@ -398,6 +421,18 @@ static void unregister_memcg_shrinker(struct shrinker *shrinker)
> {
> }
>
> +static long count_nr_deferred_memcg(int nid, struct shrinker *shrinker,
> + struct mem_cgroup *memcg)
> +{
> + return 0;
> +}
> +
> +static long set_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
> + struct mem_cgroup *memcg)
> +{
> + return 0;
> +}
> +
> static bool cgroup_reclaim(struct scan_control *sc)
> {
> return false;
> @@ -409,6 +444,39 @@ static bool writeback_throttling_sane(struct scan_control *sc)
> }
> #endif
>
> +static long count_nr_deferred(struct shrinker *shrinker,
> + struct shrink_control *sc)
> +{
> + int nid = sc->nid;
> +
> + if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
> + nid = 0;
> +
> + if (sc->memcg &&
> + (shrinker->flags & SHRINKER_MEMCG_AWARE))
> + return count_nr_deferred_memcg(nid, shrinker,
> + sc->memcg);
> +
> + return atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
> +}
> +
> +
> +static long set_nr_deferred(long nr, struct shrinker *shrinker,
> + struct shrink_control *sc)
> +{
> + int nid = sc->nid;
> +
> + if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
> + nid = 0;
> +
> + if (sc->memcg &&
> + (shrinker->flags & SHRINKER_MEMCG_AWARE))
> + return set_nr_deferred_memcg(nr, nid, shrinker,
> + sc->memcg);
> +
> + return atomic_long_add_return(nr, &shrinker->nr_deferred[nid]);
> +}
> +
> /*
> * This misses isolated pages which are not accounted for to save counters.
> * As the data only determines if reclaim or compaction continues, it is
> @@ -545,14 +613,10 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
> long freeable;
> long nr;
> long new_nr;
> - int nid = shrinkctl->nid;
> long batch_size = shrinker->batch ? shrinker->batch
> : SHRINK_BATCH;
> long scanned = 0, next_deferred;
>
> - if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
> - nid = 0;
> -
> freeable = shrinker->count_objects(shrinker, shrinkctl);
> if (freeable == 0 || freeable == SHRINK_EMPTY)
> return freeable;
> @@ -562,7 +626,7 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
> * and zero it so that other concurrent shrinker invocations
> * don't also do this scanning work.
> */
> - nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
> + nr = count_nr_deferred(shrinker, shrinkctl);
>
> total_scan = nr;
> if (shrinker->seeks) {
> @@ -653,14 +717,9 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
> next_deferred = 0;
> /*
> * move the unused scan count back into the shrinker in a
> - * manner that handles concurrent updates. If we exhausted the
> - * scan, there is no need to do an update.
> + * manner that handles concurrent updates.
> */
> - if (next_deferred > 0)
> - new_nr = atomic_long_add_return(next_deferred,
> - &shrinker->nr_deferred[nid]);
> - else
> - new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
> + new_nr = set_nr_deferred(next_deferred, shrinker, shrinkctl);
>
> trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan);
> return freed;
>
