Messages in this thread | | | Date | Tue, 17 May 2011 09:55:46 -0400 | From | Rik van Riel <> | Subject | Re: [rfc patch 4/6] memcg: reclaim statistics |
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On 05/17/2011 03:42 AM, Johannes Weiner wrote:
> It does hierarchical soft limit reclaim once triggered, but I meant > that soft limits themselves have no hierarchical meaning. Say you > have the following hierarchy: > > root_mem_cgroup > > aaa bbb > > a1 a2 b1 b2 > > a1-1 > > Consider aaa and a1 had a soft limit. If global memory arose, aaa and > all its children would be pushed back with the current scheme, the one > you are proposing, and the one I am proposing. > > But now consider aaa hitting its hard limit. Regular target reclaim > will be triggered, and a1, a2, and a1-1 will be scanned equally from > hierarchical reclaim. That a1 is in excess of its soft limit is not > considered at all. > > With what I am proposing, a1 and a1-1 would be pushed back more > aggressively than a2, because a1 is in excess of its soft limit and > a1-1 is contributing to that.
Ying, I think Johannes has a good point. I do not see a way to enforce the limits properly with the scheme we came up with at LSF, in the hierarchical scenario above.
There may be a way, but until we think of it, I suspect it will be better to go with Johannes's scheme for now.
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