On Mon, 28 Apr 2014 14:26:41 +0200 Michal Hocko <mhocko@xxxxxxx> wrote: > Hi, > previous discussions have shown that soft limits cannot be reformed > (http://lwn.net/Articles/555249/). This series introduces an alternative > approach for protecting memory allocated to processes executing within > a memory cgroup controller. It is based on a new tunable that was > discussed with Johannes and Tejun held during the kernel summit 2013 and > at LSF 2014. > > This patchset introduces such low limit that is functionally similar > to a minimum guarantee. Memcgs which are under their lowlimit are not > considered eligible for the reclaim (both global and hardlimit) unless > all groups under the reclaimed hierarchy are below the low limit when > all of them are considered eligible. Permitting containers to avoid global reclaim sounds rather worrisome. Fairness: won't it permit processes to completely protect their memory while everything else in the system is getting utterly pounded? We need to consider global-vs-memcg fairness as well as memcg-vs-memgc. Security: can this feature be used to DoS the machine? Set up enough hierarchies which are below their low limit and we risk memory exhaustion and swap-thrashing and oom-killings for other processes. All of that being said, your statement doesn't appear to be true ;) > +static void shrink_zone(struct zone *zone, struct scan_control *sc) > +{ > + if (!__shrink_zone(zone, sc, true)) { > + /* > + * First round of reclaim didn't find anything to reclaim > + * because of low limit protection so try again and ignore > + * the low limit this time. > + */ > + __shrink_zone(zone, sc, false); > + } > } -- 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>