Re: [PATCH 1/2] Add the soft_limit reclaim in global direct reclaim.

[Ying Han <yinghan@google.com>]

On Fri, Apr 29, 2011 at 3:26 AM, Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> * Ying Han <yinghan@google.com> [2011-04-28 15:37:05]:
>
>> We recently added the change in global background reclaim which
>> counts the return value of soft_limit reclaim. Now this patch adds
>> the similar logic on global direct reclaim.
>>
>> We should skip scanning global LRU on shrink_zone if soft_limit reclaim
>> does enough work. This is the first step where we start with counting
>> the nr_scanned and nr_reclaimed from soft_limit reclaim into global
>> scan_control.
>>
>> Signed-off-by: Ying Han <yinghan@google.com>
>> ---
>>  mm/vmscan.c |   16 ++++++++++++++--
>>  1 files changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index b3a569f..84003cc 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -1959,11 +1959,14 @@ restart:
>>   * If a zone is deemed to be full of pinned pages then just give it a light
>>   * scan then give up on it.
>>   */
>> -static void shrink_zones(int priority, struct zonelist *zonelist,
>> +static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
>>                                       struct scan_control *sc)
>>  {
>>       struct zoneref *z;
>>       struct zone *zone;
>> +     unsigned long nr_soft_reclaimed;
>> +     unsigned long nr_soft_scanned;
>> +     unsigned long total_scanned = 0;
>>
>>       for_each_zone_zonelist_nodemask(zone, z, zonelist,
>>                                       gfp_zone(sc->gfp_mask), sc->nodemask) {
>> @@ -1980,8 +1983,17 @@ static void shrink_zones(int priority, struct zonelist *zonelist,
>>                               continue;       /* Let kswapd poll it */
>>               }
>>
>> +             nr_soft_scanned = 0;
>> +             nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
>> +                                                     sc->order, sc->gfp_mask,
>> +                                                     &nr_soft_scanned);
>> +             sc->nr_reclaimed += nr_soft_reclaimed;
>> +             total_scanned += nr_soft_scanned;
>> +
>>               shrink_zone(priority, zone, sc);
>>       }
>> +
>> +     return total_scanned;
>>  }
>>
>>  static bool zone_reclaimable(struct zone *zone)
>> @@ -2045,7 +2057,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
>>               sc->nr_scanned = 0;
>>               if (!priority)
>>                       disable_swap_token();
>> -             shrink_zones(priority, zonelist, sc);
>> +             total_scanned += shrink_zones(priority, zonelist, sc);
>>               /*
>>                * Don't shrink slabs when reclaiming memory from
>>                * over limit cgroups
>
> Seems reasonable to me, are you able to see the benefits of setting
> soft limits and then adding back the stats on global LRU scan if
> soft limits did a good job?

I can list the stats on my next post which shows the how many reclaimed from
soft_limit reclaim vs per-zone recalim before and after the patch.

Thanks

--Ying
>
> --
>        Three Cheers,
>        Balbir
>

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