On 10/20/2011 05:33 AM, Michal Hocko wrote:
Hi all, this is a request for discussion (I hope we can touch this during memcg meeting during the upcoming KS). I have brought this up earlier this year before LSF (http://thread.gmane.org/gmane.linux.kernel.mm/60464). The patch got much smaller since then due to excellent Johannes' memcg naturalization work (http://thread.gmane.org/gmane.linux.kernel.mm/68724) which this is based on. I realize that this will be controversial but I would like to hear whether this is strictly no-go or whether we can go that direction (the implementation might differ of course). The patch is still half baked but I guess it should be sufficient to show what I am trying to achieve. The basic idea is that memcgs would get a new attribute (isolated) which would control whether that group should be considered during global reclaim.
I'd like to hear a bit more of your use cases, but at first, I don't like it. I think we should always, regardless of any knobs or definitions, be able to globally select a task or set of tasks, and kill them.
We have a slightly similar need here (we'd have to find out how similar...). We're working on it as well, but no patches yet (very basic) Let me describe it so we can see if it fits.
The main concern is with OOM behaviour of tasks within a cgroup. We'd like to be able to, in a per-cgroup basis:
* select how "important" a group is. OOM should try to kill less important memory hogs first (but note: it's less important *memory hogs*, not ordinary processes, and all of them are actually considered) * select if a fat task within a group should be OOMed, or if the whole group should go. * assuming an hierarchical grouping, select if we should kill children first * assuming an hierarchical grouping, select if we should kill children at all.
This is a broader work, but I am under the impression that you should also be able to contemplate your needs (at least the OOM part) with such mechanism, by setting arbitrarily high limits on certain cgroups.
Of course it might be the case that I am not yet fully understanding your scenario. In this case, I'm all ears!
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