Re: Low overhead patches for the memory cgroup controller (v4)

KAMEZAWA Hiroyuki wrote:
> On Mon, 15 Jun 2009 11:18:17 +0900
> Daisuke Nishimura <nishimura <at> mxp.nes.nec.co.jp> wrote:
> 
>> On Mon, 15 Jun 2009 00:07:40 +0530, Balbir Singh <balbir <at> linux.vnet.ibm.com> wrote:
>>> Here is v4 of the patches, please review and comment
>>>
>>> Feature: Remove the overhead associated with the root cgroup
>>>
>>> From: Balbir Singh <balbir <at> linux.vnet.ibm.com>
>>>
>>> changelog v4 -> v3
>>> 1. Rebase to mmotm 9th june 2009
>>> 2. Remove PageCgroupRoot, we have account LRU flags to indicate that
>>>    we do only accounting and no reclaim.
>> hmm, I prefer the previous version of PCG_ACCT_LRU meaning. It can be
>> used to remove annoying list_empty(&pc->lru) and !pc->mem_cgroup checks.
>>
>>> 3. pcg_default_flags has been used again, since PCGF_ROOT is gone,
>>>    we set PCGF_ACCT_LRU only in mem_cgroup_add_lru_list
>> It might be safe, but I don't think it's a good idea to touch PCGF_ACCT_LRU
>> outside of zone->lru_lock.
>>
>> IMHO, the most complicated case is a SwapCache which has been read ahead by
>> a *different* cpu from the cpu doing do_swap_page(). Those SwapCache can be
>> on page_vec and be drained to LRU asymmetrically with do_swap_page().
>> Well, yes it would be safe just because PCGF_ACCT_LRU would not be set
>> if PCGF_USED has not been set, but I don't think it's a good idea to touch
>> PCGF_ACCT_LRU outside of zone->lru_lock anyway.
>>
>>
>> Doesn't a patch like below work for you ?
>> Lightly tested under global memory pressure(w/o memcg's memory pressure)
>> on a small machine(just a bit modified from then though).
>>

OK, so you like the older meaning and implementation, the code seems fine to me,
I like the removal of list_empty() checks that you and Kame have proposed.

--

-- 
	Balbir

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