[dm-devel] Re: dm-ioband + bio-cgroup benchmarks

[KAMEZAWA Hiroyuki]

On Fri, 19 Sep 2008 12:34:05 +0900 (JST)
Hirokazu Takahashi <taka at valinux.co.jp> wrote:

> I've decided to get Ryo to post the accurate dirty-page tracking patch
> for bio-cgroup, which isn't perfect yet though. The memory controller
> never wants to support this tracking because migrating a page between
> memory cgroups is really heavy.
> 
> I also thought enhancing the memory controller would be good enough,
> but a lot of people said they wanted to control memory resource and
> block I/O resource separately.
> So you can create several bio-cgroup in one memory-cgroup,
> or you can use bio-cgroup without memory-cgroup.
> 
> I also have a plan to implement more acurate tracking mechanism
> on bio-cgroup after the memory cgroup team re-implement the infrastructure,
> which won't be supported by memory-cgroup.
> When a process are moved into another memory cgroup,
> the pages belonging to the process don't move to the new cgroup
> because migrating pages is so heavy. It's hard to find the pages
> from the process and migrating pages may cause some memory pressure.
> I'll implement this feature only on bio-cgroup with minimum overhead
> 
I really would like to move page_cgroup to new cgroup when the process moves...
But it's just in my plan and I'm not sure I can do it or not.

Anyway what's next for me is
 1. fix current discussion to remove page->page_cgroup pointer.
 2. reduce locks.
 3. support swap and swap-cache.

I think algorithm for (1), (2) is now getting smart.

Thanks,
-Kame