linux-kernel - Re: [PATCH -V6 07/14] memcg: Add HugeTLB extension

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Date:	Fri, 15 Jun 2012 15:31:32 -0700
From:	Aditya Kali <adityakali@...gle.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	linux-mm@...ck.org, mgorman@...e.de, dhillf@...il.com,
	aarcange@...hat.com, mhocko@...e.cz, hannes@...xchg.org,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	Ying Han <yinghan@...gle.com>
Subject: Re: [PATCH -V6 07/14] memcg: Add HugeTLB extension

On Mon, Jun 11, 2012 at 2:23 AM, David Rientjes <rientjes@...gle.com> wrote:
> On Mon, 11 Jun 2012, Kamezawa Hiroyuki wrote:
>
>> Now, I think...
>>
>>   1. I need to agree that overhead is _not_ negligible.
>>
>>   2. THP should be the way rather than hugetlb for my main target platform.
>>      (shmem/tmpfs should support THP. we need study.)
>>      user-experience should be fixed by THP+tmpfs+memcg.
>>
>>   3. It seems Aneesh decided to have independent hugetlb cgroup.
>>
>> So, now, I admit to have independent hugetlb cgroup.
>> Other opinions ?
>>
>
> I suggested the seperate controller in the review of the patchset so I
> obviously agree with your conclusion.  I don't think we should account for
> hugetlb pages in memory.usage_in_bytes and enforce memory.limit_in_bytes
> since 512 4K pages is not the same as 1 2M page which may be a sacred
> resource if fragmentation is high.
>
Based on the usecase at Google, I see a definite value in including
hugepage usage in memory.usage_in_bytes as well and having a single
limit for memory usage for the job. Our jobs wants to specify only one
(total) memory limit (including slab usage, and other kernel memory
usage, hugepages, etc.).

The hugepage/smallpage requirements of the job vary during its
lifetime. Having two different limits means less flexibility for jobs
as they now have to specify their limit as (max_hugepage,
max_smallpage) instead of max(hugepage + smallpage). Two limits
complicates the API for the users and requires them to over-specify
the resources.

> Many thanks to Aneesh for continuing to update the patchset and working
> toward a resolution on this, I love the direction its taking.
>
> --
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Thanks,
-- 
Aditya
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