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

[Hirokazu Takahashi <taka valinux co jp>]

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.

Thanks,
Hirokazu Takahashi.