On Thu, Sep 22, 2011 at 11:30 AM, Greg Thelen<gthelen@xxxxxxxxxx> wrote:Btw: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