On 10/11/2012 05:11 PM, Michal Hocko wrote: > On Mon 08-10-12 14:06:15, Glauber Costa wrote: >> Because kmem charges can outlive the cgroup, we need to make sure that >> we won't free the memcg structure while charges are still in flight. >> For reviewing simplicity, the charge functions will issue >> mem_cgroup_get() at every charge, and mem_cgroup_put() at every >> uncharge. >> >> This can get expensive, however, and we can do better. mem_cgroup_get() >> only really needs to be issued once: when the first limit is set. In the >> same spirit, we only need to issue mem_cgroup_put() when the last charge >> is gone. >> >> We'll need an extra bit in kmem_accounted for that: KMEM_ACCOUNTED_DEAD. >> it will be set when the cgroup dies, if there are charges in the group. >> If there aren't, we can proceed right away. >> >> Our uncharge function will have to test that bit every time the charges >> drop to 0. Because that is not the likely output of >> res_counter_uncharge, this should not impose a big hit on us: it is >> certainly much better than a reference count decrease at every >> operation. >> >> [ v3: merged all lifecycle related patches in one ] >> >> Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx> >> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> >> CC: Christoph Lameter <cl@xxxxxxxxx> >> CC: Pekka Enberg <penberg@xxxxxxxxxxxxxx> >> CC: Michal Hocko <mhocko@xxxxxxx> >> CC: Johannes Weiner <hannes@xxxxxxxxxxx> >> CC: Suleiman Souhlal <suleiman@xxxxxxxxxx> > > OK, I like the optimization. I have just one comment to the > memcg_kmem_dead naming but other than that > > Acked-by: Michal Hocko <mhocko@xxxxxxx> > > [...] >> +static bool memcg_kmem_dead(struct mem_cgroup *memcg) > > The name is tricky because it doesn't tell you that it clears the flag > which made me scratch my head when reading comment in kmem_cgroup_destroy > memcg_kmem_finally_kill_that_bastard() ? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>