linux-kernel - Re: [PATCH 08/10] mm: Set bit in memcg shrinker bitmap on first list

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 26 Mar 2018 18:31:12 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     Vladimir Davydov <vdavydov.dev@...il.com>
Cc:     viro@...iv.linux.org.uk, hannes@...xchg.org, mhocko@...nel.org,
        akpm@...ux-foundation.org, tglx@...utronix.de,
        pombredanne@...b.com, stummala@...eaurora.org,
        gregkh@...uxfoundation.org, sfr@...b.auug.org.au, guro@...com,
        mka@...omium.org, penguin-kernel@...ove.SAKURA.ne.jp,
        chris@...is-wilson.co.uk, longman@...hat.com, minchan@...nel.org,
        hillf.zj@...baba-inc.com, ying.huang@...el.com,
        mgorman@...hsingularity.net, shakeelb@...gle.com, jbacik@...com,
        linux@...ck-us.net, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, willy@...radead.org
Subject: Re: [PATCH 08/10] mm: Set bit in memcg shrinker bitmap on first
 list_lru item apearance

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@...tuozzo.com>
>> ---
>>  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