On Tue, Jan 24, 2012 at 12:44 AM, Ying Han <yinghan@xxxxxxxxxx> wrote: > On Mon, Jan 23, 2012 at 5:02 AM, Michal Hocko <mhocko@xxxxxxx> wrote: >> On Sat 21-01-12 22:49:23, Hillf Danton wrote: >>> In soft limit reclaim, overreclaim occurs when pages are reclaimed from mem >>> group that is under its soft limit, or when more pages are reclaimd than the >>> exceeding amount, then performance of reclaimee goes down accordingly. >> >> First of all soft reclaim is more a help for the global memory pressure >> balancing rather than any guarantee about how much we reclaim for the >> group. >> We need to do more changes in order to make it a guarantee. >> For example you implementation will cause severe problems when all >> cgroups are soft unlimited (default conf.) or when nobody is above the >> limit but the total consumption triggers the global reclaim. Therefore >> nobody is in excess and you would skip all groups and only bang on the >> root memcg. >> True, ideally soft reclaim should not turn on and allow global reclaim to occur in the scenario mentioned. >> Ying Han has a patch which basically skips all cgroups which are under >> its limit until we reach a certain reclaim priority but even for this we >> need some additional changes - e.g. reverse the current default setting >> of the soft limit. >> I'd be wary of that approach, because it might be harder to explain the working of soft limits,I'll look at the discussion thread mentioned earlier for the benefits of that approach. >> Anyway, I like the nr_to_reclaim reduction idea because we have to do >> this in some way because the global reclaim starts with ULONG >> nr_to_scan. > > Agree with Michal where there are quite a lot changes we need to get > in for soft limit before any further optimization. > > Hillf, please refer to the patch from Johannes > https://lkml.org/lkml/2012/1/13/99 which got quite a lot recent > discussions. I am expecting to get that in before further soft limit > changes. Balbir -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>