On 24.03.2018 22:45, Vladimir Davydov wrote:
> On Wed, Mar 21, 2018 at 04:22:40PM +0300, Kirill Tkhai wrote:
>> Introduce set_shrinker_bit() function to set shrinker-related
>> bit in memcg shrinker bitmap, and set the bit after the first
>> item is added and in case of reparenting destroyed memcg's items.
>>
>> This will allow next patch to make shrinkers be called only,
>> in case of they have charged objects at the moment, and
>> to improve shrink_slab() performance.
>>
>> Signed-off-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
>> ---
>> include/linux/shrinker.h | 7 +++++++
>> mm/list_lru.c | 22 ++++++++++++++++++++--
>> mm/vmscan.c | 7 +++++++
>> 3 files changed, 34 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
>> index 738de8ef5246..24aeed1bc332 100644
>> --- a/include/linux/shrinker.h
>> +++ b/include/linux/shrinker.h
>> @@ -78,4 +78,11 @@ struct shrinker {
>>
>> extern __must_check int register_shrinker(struct shrinker *);
>> extern void unregister_shrinker(struct shrinker *);
>> +#if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
>> +extern void set_shrinker_bit(struct mem_cgroup *, int, int);
>> +#else
>> +static inline void set_shrinker_bit(struct mem_cgroup *memcg, int node, int id)
>> +{
>> +}
>> +#endif
>
> IMO this function, as well as other shrinker bitmap manipulation
> functions, should be defined in memcontrol.[hc] and have mem_cgroup_
> prefix.
>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index 9d1df5d90eca..265cf069b470 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -378,6 +378,13 @@ static void del_shrinker(struct shrinker *shrinker)
>> list_del(&shrinker->list);
>> up_write(&shrinker_rwsem);
>> }
>> +
>> +void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int nr)
>> +{
>> + struct shrinkers_map *map = SHRINKERS_MAP(memcg);
>> +
>> + set_bit(nr, map->map[nid]);
>> +}
>
> Shouldn't we use rcu_read_lock here? After all, the map can be
> reallocated right from under our feet.
We do have to do that! Thanks for pointing.
Kirill
