[dm-devel] Re: [PATCH 4/7] bio-cgroup: Split the cgroup memory subsystem into two parts

[Balbir Singh <balbir linux vnet ibm com>]

Hirokazu Takahashi wrote:
> Hi,
> 
>>>> I'm now writing remove-lock-page-cgroup patches. it works well.
>>>> please wait for a while...
>>> I'm looking forward to those patches.
>>>
>>> By the way, I'm glad if memory-cgroup has a feature which can make a
>>> page_cgroup move between cgroups with small overhead. It makes
>>> bio-cgroup improve the accuracy of tracking down pages.
>> Page movement can be a very expensive operation and is proportional to the size
>> of the control group. I think movement should be an optional feature, if we ever
>> add it.
> 
> Yes, we should avoid moving pages as far as it is balanced fairly well
> between groups.
> 
> But I want to move pages between bio-cgoups in case it started charging
> quite a few I/O requests to a wrong bio-cgroup. I think it will be okay
> if pages moves between bio-cgroups, but they don't need to move between
> memory cgroups. I know the latter is really heavy and the effect seems
> to be so limited.

I was under the impression that you wanted memory-cgroup to provide the page
movement feature. That is not on the TODO list for us now.

-- 
	Balbir