On Wed, 17 Aug 2011 13:35:50 +0200
Michal Hocko [off-list ref] wrote:

On Wed 17-08-11 09:54:05, KAMEZAWA Hiroyuki wrote:

quoted

On Thu, 11 Aug 2011 16:50:55 +0200
Michal Hocko [off-list ref] wrote:

quoted

What about this (just compile tested)?
--- 
From: Michal Hocko <redacted>
Subject: memcg: add nr_pages argument for hierarchical reclaim

Now that we are doing memcg direct reclaim limited to nr_to_reclaim
pages (introduced by "memcg: stop vmscan when enough done.") we have to
be more careful. Currently we are using SWAP_CLUSTER_MAX which is OK for
most callers but it might cause failures for limit resize or force_empty
code paths on big NUMA machines.

Previously we might have reclaimed up to nr_nodes * SWAP_CLUSTER_MAX
while now we have it at SWAP_CLUSTER_MAX. Both resize and force_empty rely
on reclaiming a certain amount of pages and retrying if their condition is
still not met.

Let's add nr_pages argument to mem_cgroup_hierarchical_reclaim which will
push it further to try_to_free_mem_cgroup_pages. We still fall back to
SWAP_CLUSTER_MAX for small requests so the standard code (hot) paths are not
affected by this.

Open questions:
- Should we care about soft limit as well? Currently I am using excess
  number of pages for the parameter so it can replace direct query for
  the value in mem_cgroup_hierarchical_reclaim but should we push it to
  mem_cgroup_shrink_node_zone?
  I do not think so because we should try to reclaim from more groups in the
  hierarchy and also it doesn't get to shrink_zones which has been modified
  by the previous patch.

quoted

- mem_cgroup_force_empty asks for reclaiming all pages. I guess it should be
  OK but will have to think about it some more.

force_empty/rmdir() is allowed to be stopped by Ctrl-C. I think passing res->usage
is overkilling.

So, how many pages should be reclaimed then?

How about (1 << (MAX_ORDER-1))/loop ?

Thanks,
-Kame

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