Re: [PATCH v3 2/7] socket: initial cgroup code.
From: Glauber Costa
Date: Sat Sep 24 2011 - 10:45:46 EST
On 09/22/2011 12:09 PM, Balbir Singh wrote:
On Thu, Sep 22, 2011 at 11:30 AM, Greg Thelen<gthelen@xxxxxxxxxx> wrote:
On Wed, Sep 21, 2011 at 11:59 AM, Glauber Costa<glommer@xxxxxxxxxxxxx> wrote:
Right now I am working under the assumption that tasks are long lived inside
the cgroup. Migration potentially introduces some nasty locking problems in
the mem_schedule path.
Also, unless I am missing something, the memcg already has the policy of
not carrying charges around, probably because of this very same complexity.
True that at least it won't EBUSY you... But I think this is at least a way
to guarantee that the cgroup under our nose won't disappear in the middle of
our allocations.
Here's the memcg user page behavior using the same pattern:
1. user page P is allocate by task T in memcg M1
2. T is moved to memcg M2. The P charge is left behind still charged
to M1 if memory.move_charge_at_immigrate=0; or the charge is moved to
M2 if memory.move_charge_at_immigrate=1.
3. rmdir M1 will try to reclaim P (if P was left in M1). If unable to
reclaim, then P is recharged to parent(M1).
We also have some magic in page_referenced() to remove pages
referenced from different containers. What we do is try not to
penalize a cgroup if another cgroup is referencing this page and the
page under consideration is being reclaimed from the cgroup that
touched it.
Balbir Singh
Do you guys see it as a showstopper for this series to be merged, or can
we just TODO it ?
I can push a proposal for it, but it would be done in a separate patch
anyway. Also, we may be in better conditions to fix this when the slab
part is merged - since it will likely have the same problems...
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