From: Balbir Singh <bsingharora@gmail.com>
To: Johannes Weiner <hannes@cmpxchg.org>, Zhao Hui Ding <dingzhh@cn.ibm.com>
Cc: Tejun Heo <tj@kernel.org>, cgroups@vger.kernel.org, linux-mm@kvack.org
Subject: Re: memory.force_empty is deprecated
Date: Thu, 17 Nov 2016 21:39:41 +1100 [thread overview]
Message-ID: <5b03def0-2dc4-842f-0d0e-53cc2d94936f@gmail.com> (raw)
In-Reply-To: <20161104152103.GC8825@cmpxchg.org>
On 05/11/16 02:21, Johannes Weiner wrote:
> Hi,
>
> On Fri, Nov 04, 2016 at 04:24:25PM +0800, Zhao Hui Ding wrote:
>> Hello,
>>
>> I'm Zhaohui from IBM Spectrum LSF development team. I got below message
>> when running LSF on SUSE11.4, so I would like to share our use scenario
>> and ask for the suggestions without using memory.force_empty.
>>
>> memory.force_empty is deprecated and will be removed. Let us know if it is
>> needed in your usecase at linux-mm@kvack.org
>>
>> LSF is a batch workload scheduler, it uses cgroup to do batch jobs
>> resource enforcement and accounting. For each job, LSF creates a cgroup
>> directory and put job's PIDs to the cgroup.
>>
>> When we implement LSF cgroup integration, we found creating a new cgroup
>> is much slower than renaming an existing cgroup, it's about hundreds of
>> milliseconds vs less than 10 milliseconds.
>
We added force_empty a long time back so that we could force delete
cgroups. There was no definitive way of removing references to the cgroup
from page_cgroup otherwise.
> Cgroup creation/deletion is not expected to be an ultra-hot path, but
> I'm surprised it takes longer than actually reclaiming leftover pages.
>
> By the time the jobs conclude, how much is usually left in the group?
>
> That said, is it even necessary to pro-actively remove the leftover
> cache from the group before starting the next job? Why not leave it
> for the next job to reclaim it lazily should memory pressure arise?
> It's easy to reclaim page cache, and the first to go as it's behind
> the next job's memory on the LRU list.
It might actually make sense to migrate all tasks out and check what
the left overs look like -- should be easy to reclaim. Also be mindful
if you are using v1 and have use_hierarchy set.
Balbir Singh.
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next prev parent reply other threads:[~2016-11-17 10:39 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-04 8:24 memory.force_empty is deprecated Zhao Hui Ding
2016-11-04 15:21 ` Johannes Weiner
2016-11-17 10:13 ` Zhao Hui Ding
2016-11-22 15:20 ` Michal Hocko
2016-11-17 10:39 ` Balbir Singh [this message]
2016-11-18 6:28 ` Zhao Hui Ding
2016-11-18 22:08 ` Balbir Singh
2016-11-22 15:21 ` Michal Hocko
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