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

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?

quoted

@@ -2332,7 +2332,8 @@ static int mem_cgroup_do_charge(struct m
 		return CHARGE_WOULDBLOCK;
 
 	ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, NULL,
-					      gfp_mask, flags, NULL);
+					      gfp_mask, flags, NULL,
+					      nr_pages);

Hmm, in usual, nr_pages = batch = CHARGE_BATCH = 32 ? At allocating Hugepage,
this nr_pages will be 512 ? I think it's too big...

Yes it is. I have posted updated version already:
http://www.spinics.net/lists/linux-mm/msg23113.html

Thanks,
-Kame

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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