linux-kernel - Re: [PATCH -V4 04/10] memcg: Add HugeTLB extension

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Date:	Wed, 21 Mar 2012 10:18:43 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Glauber Costa <glommer@...allels.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	linux-mm@...ck.org, mgorman@...e.de, dhillf@...il.com,
	aarcange@...hat.com, mhocko@...e.cz, akpm@...ux-foundation.org,
	hannes@...xchg.org, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org
Subject: Re: [PATCH -V4 04/10] memcg: Add HugeTLB extension

Glauber Costa <glommer@...allels.com> writes:

> On 03/19/2012 11:00 AM, KAMEZAWA Hiroyuki wrote:
>> (2012/03/19 15:52), Aneesh Kumar K.V wrote:
>>
>>>
>>>>> +#ifdef CONFIG_MEM_RES_CTLR_HUGETLB
>>>>> +static bool mem_cgroup_have_hugetlb_usage(struct mem_cgroup *memcg)
>>>>> +{
>>>>> +	int idx;
>>>>> +	for (idx = 0; idx<  hugetlb_max_hstate; idx++) {
>>>>> +		if (memcg->hugepage[idx].usage>  0)
>>>>> +			return 1;
>>>>> +	}
>>>>> +	return 0;
>>>>> +}
>>>>
>>>>
>>>> Please use res_counter_read_u64() rather than reading the value directly.
>>>>
>>>
>>> The open-coded variant is mostly derived from mem_cgroup_force_empty. I
>>> have updated the patch to use res_counter_read_u64.
>>>
>>
>> Ah, ok. it's(maybe) my bad. I'll schedule a fix.
>>
> Kame,
>
> I actually have it ready here. I can submit it if you want.
>
> This one has bitten me as well when I was trying to experiment with the 
> res_counter performance...

Do we really need memcg.res.usage to be accurate in that while loop ? If
we miss a zero update because we encountered a partial update; in the
next loop we will find it zero right ?

-aneesh

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