Re: [PATCH RFC] xfs, memcg: Call xfs_fs_nr_cached_objects() only in case of global reclaim

[Kirill Tkhai <ktkhai@virtuozzo.com>]

On 15.03.2018 22:32, Michal Hocko wrote:
> On Thu 15-03-18 22:28:43, Kirill Tkhai wrote:
>> On 15.03.2018 20:49, Michal Hocko wrote:
>>> On Thu 15-03-18 18:01:34, Kirill Tkhai wrote:
>>>> xfs_reclaim_inodes_count(XFS_M(sb)) does not care about memcg.
>>>> So, it's called for memcg reclaim too, e.g. this list is shrinked
>>>> disproportionality to another lists.
>>>>
>>>> This looks confusing, so I'm reporting about this.
>>>> Consider this patch as RFC.
>>>
>>> Could you be more specific about the problem you are trying to solve?
>>> Because we do skip shrinkers which are not memcg aware by
>>> shrink_slab:
>>> 		/*
>>> 		 * If kernel memory accounting is disabled, we ignore
>>> 		 * SHRINKER_MEMCG_AWARE flag and call all shrinkers
>>> 		 * passing NULL for memcg.
>>> 		 */
>>> 		if (memcg_kmem_enabled() &&
>>> 		    !!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE))
>>> 			continue;
>>>
>>> Or am I missing something?
>>
>> sb->s_op->nr_cached_objects is a sub-method of generic super_cache_count().
>> super_cache_count() is owned and only called by superblock's shrinker,
>> which does have SHRINKER_MEMCG_AWARE flag.
> 
> Ohh, I see. I thought it was a standard "top-level" shrinker.

There are one more in addition (it has to go in this patch):

.free_cached_objects    = xfs_fs_free_cached_objects

which is not memcg aware. It also needs to have the same fix,
if xfs_reclaim_inodes_count() is need.

Kirill