From: Shakeel Butt <shakeelb@google.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
Andrew Morton <akpm@linux-foundation.org>,
Cgroups <cgroups@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>
Subject: Re: [PATCH v5 2/2] mm/memcontrol.c: Reduce reclaim retries in mem_cgroup_resize_limit()
Date: Fri, 19 Jan 2018 06:49:29 -0800 [thread overview]
Message-ID: <CALvZod7HS6P0OU6Rps8JeMJycaPd4dF5NjxV8k1y2-yosF2bdA@mail.gmail.com> (raw)
In-Reply-To: <20180119133510.GD6584@dhcp22.suse.cz>
On Fri, Jan 19, 2018 at 5:35 AM, Michal Hocko <mhocko@kernel.org> wrote:
> On Fri 19-01-18 16:25:44, Andrey Ryabinin wrote:
>> Currently mem_cgroup_resize_limit() retries to set limit after reclaiming
>> 32 pages. It makes more sense to reclaim needed amount of pages right away.
>>
>> This works noticeably faster, especially if 'usage - limit' big.
>> E.g. bringing down limit from 4G to 50M:
>>
>> Before:
>> # perf stat echo 50M > memory.limit_in_bytes
>>
>> Performance counter stats for 'echo 50M':
>>
>> 386.582382 task-clock (msec) # 0.835 CPUs utilized
>> 2,502 context-switches # 0.006 M/sec
>>
>> 0.463244382 seconds time elapsed
>>
>> After:
>> # perf stat echo 50M > memory.limit_in_bytes
>>
>> Performance counter stats for 'echo 50M':
>>
>> 169.403906 task-clock (msec) # 0.849 CPUs utilized
>> 14 context-switches # 0.083 K/sec
>>
>> 0.199536900 seconds time elapsed
>
> But I am not going ack this one. As already stated this has a risk
> of over-reclaim if there a lot of charges are freed along with this
> shrinking. This is more of a theoretical concern so I am _not_ going to
If you don't mind, can you explain why over-reclaim is a concern at
all? The only side effect of over reclaim I can think of is the job
might suffer a bit over (more swapins & pageins). Shouldn't this be
within the expectation of the user decreasing the limits?
> nack. If we ever see such a problem then reverting this patch should be
> pretty straghtforward.
>
>> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
>> Cc: Shakeel Butt <shakeelb@google.com>
>> Cc: Michal Hocko <mhocko@kernel.org>
>> Cc: Johannes Weiner <hannes@cmpxchg.org>
>> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
>> ---
>> mm/memcontrol.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 9d987f3e79dc..09bac2df2f12 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -2448,6 +2448,7 @@ static DEFINE_MUTEX(memcg_limit_mutex);
>> static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
>> unsigned long limit, bool memsw)
>> {
>> + unsigned long nr_pages;
>> bool enlarge = false;
>> int ret;
>> bool limits_invariant;
>> @@ -2479,8 +2480,9 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
>> if (!ret)
>> break;
>>
>> - if (!try_to_free_mem_cgroup_pages(memcg, 1,
>> - GFP_KERNEL, !memsw)) {
>> + nr_pages = max_t(long, 1, page_counter_read(counter) - limit);
>> + if (!try_to_free_mem_cgroup_pages(memcg, nr_pages,
>> + GFP_KERNEL, !memsw)) {
>> ret = -EBUSY;
>> break;
>> }
>> --
>> 2.13.6
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@kvack.org. For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
>
> --
> Michal Hocko
> SUSE Labs
--
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next prev parent reply other threads:[~2018-01-19 14:49 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-20 10:24 [PATCH 1/2] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Andrey Ryabinin
2017-12-20 10:24 ` [PATCH 2/2] mm/memcg: Consolidate mem_cgroup_resize_[memsw]_limit() functions Andrey Ryabinin
2017-12-20 10:33 ` [PATCH 1/2] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Michal Hocko
2017-12-20 11:32 ` Andrey Ryabinin
2017-12-20 11:34 ` Michal Hocko
2017-12-20 18:15 ` Shakeel Butt
2017-12-21 10:00 ` Andrey Ryabinin
2017-12-20 13:21 ` [PATCH v2 " Andrey Ryabinin
2017-12-20 13:21 ` [PATCH v2 2/2] mm/memcg: Consolidate mem_cgroup_resize_[memsw]_limit() functions Andrey Ryabinin
2017-12-20 13:53 ` [PATCH v2 1/2] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Michal Hocko
2018-01-09 16:58 ` [PATCH v3 " Andrey Ryabinin
2018-01-09 16:58 ` [PATCH v3 2/2] mm/memcg: Consolidate mem_cgroup_resize_[memsw]_limit() functions Andrey Ryabinin
2018-01-09 17:10 ` Shakeel Butt
2018-01-09 17:26 ` Andrey Ryabinin
2018-01-09 23:26 ` Andrew Morton
2018-01-10 12:43 ` [PATCH v4] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Andrey Ryabinin
2018-01-10 22:31 ` Andrew Morton
2018-01-11 11:59 ` Andrey Ryabinin
2018-01-12 0:21 ` Andrew Morton
2018-01-12 9:08 ` Andrey Ryabinin
2018-01-11 10:42 ` Michal Hocko
2018-01-11 12:21 ` Andrey Ryabinin
2018-01-11 12:46 ` Michal Hocko
2018-01-11 15:23 ` Andrey Ryabinin
2018-01-11 16:29 ` Michal Hocko
2018-01-11 21:59 ` Andrey Ryabinin
2018-01-12 12:24 ` Michal Hocko
2018-01-12 22:57 ` Shakeel Butt
2018-01-15 12:29 ` Andrey Ryabinin
2018-01-15 17:04 ` Shakeel Butt
2018-01-15 12:30 ` Andrey Ryabinin
2018-01-15 12:46 ` Michal Hocko
2018-01-15 12:53 ` Andrey Ryabinin
2018-01-15 12:58 ` Michal Hocko
2018-01-09 17:08 ` [PATCH v3 1/2] " Andrey Ryabinin
2018-01-09 17:22 ` Shakeel Butt
2018-01-19 13:25 ` [PATCH v5 1/2] mm/memcontrol.c: " Andrey Ryabinin
2018-01-19 13:25 ` [PATCH v5 2/2] mm/memcontrol.c: Reduce reclaim retries in mem_cgroup_resize_limit() Andrey Ryabinin
2018-01-19 13:35 ` Michal Hocko
2018-01-19 14:49 ` Shakeel Butt [this message]
2018-01-19 15:11 ` Michal Hocko
2018-01-19 15:24 ` Shakeel Butt
2018-01-19 15:31 ` Michal Hocko
2018-02-21 20:17 ` Andrew Morton
2018-02-22 13:50 ` Andrey Ryabinin
2018-02-22 14:09 ` Michal Hocko
2018-02-22 15:13 ` Andrey Ryabinin
2018-02-22 15:33 ` Michal Hocko
2018-02-22 15:38 ` Andrey Ryabinin
2018-02-22 15:44 ` Michal Hocko
2018-02-22 16:01 ` Andrey Ryabinin
2018-02-22 16:30 ` Michal Hocko
2018-01-19 13:32 ` [PATCH v5 1/2] mm/memcontrol.c: try harder to decrease [memory,memsw].limit_in_bytes Michal Hocko
2018-01-25 19:44 ` Andrey Ryabinin
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