linux-kernel - Re: [PATCH] memcg: rework inactive

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Date:	Thu, 16 Feb 2012 10:57:14 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] memcg: rework inactive_ratio logic

KAMEZAWA Hiroyuki wrote:
> On Wed, 15 Feb 2012 20:24:42 +0400
> Konstantin Khlebnikov<khlebnikov@...nvz.org>  wrote:
>
>> This patch adds mem_cgroup->inactive_ratio calculated from hierarchical memory limit.
>> It updated at each limit change before shrinking cgroup to this new limit.
>> Ratios for all child cgroups are updated too, because parent limit can affect them.
>> Update precedure can be greatly optimized if its performance becomes the problem.
>> Inactive ratio for unlimited or huge limit does not matter, because we'll never hit it.
>>
>> At global reclaim always use global ratio from zone->inactive_ratio.
>> At mem-cgroup reclaim use inactive_ratio from target memory cgroup,
>> this is cgroup which hit its limit and cause this reclaimer invocation.
>>
>> Thus, global memory reclaimer will try to keep ratio for all lru lists in zone
>> above one mark, this guarantee that total ratio in this zone will be above too.
>> Meanwhile mem-cgroup will do the same thing for its lru lists in all zones, and
>> for all lru lists in all sub-cgroups in hierarchy.
>>
>> Also this patch removes some redundant code.
>>
>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@...nvz.org>
>
> Hmm, the main purpose of this patch is to remove calculation per get_scan_ratio() ?

Technically, it was preparation for "mm: unify inactive_list_is_low()" from "memory book keeping" patchset.
So, actually its main purpose is moving all active/inactive size calculation to mm/vmscan.c

Also I trying to figure out most sane logic for inactive_ratio calculation,
currently global memory reclaimer sometimes uses memcg-calculated ratio, it looks strange.

>> ---
>>   include/linux/memcontrol.h |   16 ++------
>>   mm/memcontrol.c            |   85 ++++++++++++++++++++++++--------------------
>>   mm/vmscan.c                |   82 +++++++++++++++++++++++-------------------
>>   3 files changed, 93 insertions(+), 90 deletions(-)
>>   static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
>>                                unsigned long long val)
>>   {

<cut>

>> @@ -3422,6 +3416,7 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
>>                        else
>>                                memcg->memsw_is_minimum = false;
>>                }
>> +             mem_cgroup_update_inactive_ratio(memcg, val);
>>                mutex_unlock(&set_limit_mutex);
>>
>>                if (!ret)
>> @@ -3439,6 +3434,12 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
>>        if (!ret&&  enlarge)
>>                memcg_oom_recover(memcg);
>>
>> +     if (ret) {
>> +             mutex_lock(&set_limit_mutex);
>> +             mem_cgroup_update_inactive_ratio(memcg, RESOURCE_MAX);
>> +             mutex_unlock(&set_limit_mutex);
>> +     }
>
> Why RESOUECE_MAX ?

resize was failed, so we return back normal value calculated from the current limit.
target == RESOURCE_MAX isn't clip limit: min(RESOURCE_MAX, limit) == limit

>
> Thanks,
> -Kame
>
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