Re: [PATCH -mmotm 0/8] memcg: recharge at task move

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Fri, 6 Nov 2009 14:10:11 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> Hi.
> 
> In current memcg, charges associated with a task aren't moved to the new cgroup
> at task move. These patches are for this feature, that is, for recharging to
> the new cgroup and, of course, uncharging from old cgroup at task move.
> 
> Current virsion supports only recharge of non-shared(mapcount == 1) anonymous pages
> and swaps of those pages. I think it's enough as a first step.
> 
> [1/8] cgroup: introduce cancel_attach()
> [2/8] memcg: move memcg_tasklist mutex
> [3/8] memcg: add mem_cgroup_cancel_charge()
> [4/8] memcg: cleanup mem_cgroup_move_parent()
> [5/8] memcg: add interface to recharge at task move
> [6/8] memcg: recharge charges of anonymous page
> [7/8] memcg: avoid oom during recharge at task move
> [8/8] memcg: recharge charges of anonymous swap
> 
> 2 is dependent on 1 and 4 is dependent on 3.
> 3 and 4 are just for cleanups.
> 5-8 are the body of this feature.
> 
> Major Changes from Oct13:
> - removed "[RFC]".
> - rebased on mmotm-2009-11-01-10-01.
> - dropped support for file cache and shmem/tmpfs(revisit in future).
> - Updated Documentation/cgroup/memory.txt.
> 

Seems much nicer but I have some nitpicks as already commented.

For [8/8], mm->swap_usage counter may be a help for making it faster.
Concern is how it's shared but will not be very big error.

> TODO:
> - add support for file cache, shmem/tmpfs, and shared(mapcount > 1) pages.
> - implement madvise(2) to let users decide the target vma for recharge.
> 

About this, I think "force_move_shared_account" flag is enough, I think.
But we have to clarify "mmap()ed but not on page table" entries are not
moved....

Thanks,
-Kame




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