On 29.01.2021 17:55, Kirill Tkhai wrote:
> 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.
Hm, I see you already introduced a helper in [10/11], but it is used in only place.
Then, we should use it for all places (introduce the helper earlier).
>> /* 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;
>>
>
