Re: [patch v3 -mm 1/3] memcg: integrate soft reclaim tighter with zone shrinking code

[Tejun Heo <tj@kernel.org>]

Hello,

On Fri, May 17, 2013 at 10:27 AM, Johannes Weiner <hannes@cmpxchg.org> wrote:
>>Hmmm... if the iteration is the problem, it shouldn't be difficult to
>>build list of children which should be iterated.  Would that make it
>>acceptable?
>
> You mean, a separate structure that tracks which groups are in excess of the limit?  Like the current tree? :)

Heh, yeah, realized that after writing it but it can be something much
simpler. ie. just linked list of children with soft limit configured.

> Kidding aside, yes, that would be better, and an unsorted list would probably be enough for the global case.

Yeap.

> To support target reclaim soft limits later on, we could maybe propagate tags upwards the cgroup tree when a group is in excess so that reclaim can be smarter about which subtrees to test for soft limits and which to skip during the soft limit pass.  The no-softlimit-set-anywhere case is then only a single tag test in the root cgroup.
>
> But starting with the list would be simple enough, delete a bunch of code, come with the same performance improvements etc.

Thanks.

--
tejun