On Tue, 21 Feb 2012 15:34:36 +0400 Glauber Costa <glommer@xxxxxxxxxxxxx> wrote: > In the context of tracking kernel memory objects to a cgroup, the > following problem appears: we may need to destroy a cgroup, but > this does not guarantee that all objects inside the cache are dead. > This can't be guaranteed even if we shrink the cache beforehand. > > The simple option is to simply leave the cache around. However, > intensive workloads may have generated a lot of objects and thus > the dead cache will live in memory for a long while. > > Scanning the list of objects in the dead cache takes time, and > would probably require us to lock the free path of every objects > to make sure we're not racing against the update. > > I decided to give a try to a different idea then - but I'd be > happy to pursue something else if you believe it would be better. > > Upon memcg destruction, all the pages on the partial list > are moved to the new slab (usually the parent memcg, or root memcg) > When an object is freed, there are high stakes that no list locks > are needed - so this case poses no overhead. If list manipulation > is indeed needed, we can detect this case, and perform it > in the right slab. > > If all pages were residing in the partial list, we can free > the cache right away. Otherwise, we do it when the last cache > leaves the full list. > How about starting from 'don't handle slabs on dead memcg' if shrink_slab() can find them.... This "move" complicates all implementation, I think... Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
