On 09/26/2011 07:52 AM, KAMEZAWA Hiroyuki wrote:
On Sat, 24 Sep 2011 11:45:04 -0300
Glauber Costa<glommer@xxxxxxxxxxxxx> wrote:
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 ?
In my experience, 'I can't rmdir cgroup.' is always an important/difficult
problem. The users cannot know where the accouting is leaking other than
kmem.usage_in_bytes or memory.usage_in_bytes. and can't fix the issue.
please add EXPERIMENTAL to Kconfig until this is fixed.
I am working on something here that may allow it.
But I think it is independent of the rest, and I can repost the series
fixing the problems raised here without it, + EXPERIMENTAL.
Btw, using EXPERIMENTAL here is a very good idea. I think that we should
turn EXPERIMENTAL on even if I fix for that exists, for a least a couple
of months until we see how this thing really evolves.
What do you think?
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...
Yes. considering sockets which can be shared between tasks(cgroups)
you'll finally need
- owner task of socket
- account moving callback
Or disallow task moving once accounted.
I personally think disallowing task movement once accounted is
reasonable. At least for starters.
I think I can add at least that to the next proposal. Famous last words
is, it should not be that hard...
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