linux-kernel - Re: [PATCH 5/7] memcg: get rid of once-per-second cache shrinking for dead memcgs

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Message-ID: <50A5E997.6060002@jp.fujitsu.com>
Date:	Fri, 16 Nov 2012 16:21:59 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Glauber Costa <glommer@...allels.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>
Subject: Re: [PATCH 5/7] memcg: get rid of once-per-second cache shrinking
 for dead memcgs

(2012/11/16 16:11), Glauber Costa wrote:
> On 11/16/2012 09:07 AM, Kamezawa Hiroyuki wrote:
>> (2012/11/15 22:47), Glauber Costa wrote:
>>> On 11/15/2012 01:41 PM, Kamezawa Hiroyuki wrote:
>>>> (2012/11/15 11:54), Glauber Costa wrote:
>>>>> The idea is to synchronously do it, leaving it up to the shrinking
>>>>> facilities in vmscan.c and/or others. Not actively retrying shrinking
>>>>> may leave the caches alive for more time, but it will remove the ugly
>>>>> wakeups. One would argue that if the caches have free objects but are
>>>>> not being shrunk, it is because we don't need that memory yet.
>>>>>
>>>>> Signed-off-by: Glauber Costa <glommer@...allels.com>
>>>>> CC: Michal Hocko <mhocko@...e.cz>
>>>>> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>>>>> CC: Johannes Weiner <hannes@...xchg.org>
>>>>> CC: Andrew Morton <akpm@...ux-foundation.org>
>>>>
>>>> I agree this patch but can we have a way to see the number of unaccounted
>>>> zombie cache usage for debugging ?
>>>>
>>>> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>>>>
>>> Any particular interface in mind ?
>>>
>>
>> Hmm, it's debug interface and having cgroup file may be bad.....
>> If it can be seen in bytes or some, /proc/vmstat ?
>>
>> out_of_track_slabs  xxxxxxx. hm ?
>>
> 
> I particularly think that, being this a debug interface, it is also
> useful to have an indication of which caches are still in place. This is
> because the cache itself, is the best indication we have about the
> specific workload that may be keeping it in memory.
> 
> I first thought debugfs could help us probing useful information out of
> it, but given all the abuse people inflicted in debugfs... maybe we
> could have a file in the root memcg with that information for all
> removed memcgs? If we do that, we can go further and list the memcgs
> that are pending due to memsw as well. memory.dangling_memcgs ?
> 

Hm, I'm ok with it... others ?

Thanks,
-Kame




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