Re: [PATCH v5 2/2] mm/memcontrol.c: Reduce reclaim retries in mem_cgroup_resize_limit()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Fri, Jan 19, 2018 at 5:35 AM, Michal Hocko <mhocko@xxxxxxxxxx> 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@xxxxxxxxxxxxx>

Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>

>> Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
>> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
>> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
>> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
>> ---
>>  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@xxxxxxxxx.  For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
>
> --
> Michal Hocko
> SUSE Labs
--
To unsubscribe from this list: send the line "unsubscribe cgroups" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Security]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]     [Monitors]

  Powered by Linux