On Tue 29-03-11 21:15:59, Zhu Yanhai wrote: > Michal, Hi, > Maybe what we need here is some kind of trade-off? > Let's say a new configuable parameter reserve_limit, for the cgroups > which want to > have some guarantee in the memory resource, we have: > > limit_in_bytes > soft_limit > reserve_limit > > MEM[limit_in_bytes..soft_limit] are the bytes that I'm willing to contribute > to the others if they are short of memory. > > MEM[soft_limit..reserve_limit] are the bytes that I can afford if the others > are still eager for memory after I gave them MEM[limit_in_bytes..soft_limit]. > > MEM[reserve_limit..0] are the bytes which is a must for me to guarantee QoS. > Nobody is allowed to steal them. > > And reserve_limit is 0 by default for the cgroups who don't care about Qos. > > Then the reclaim path also needs some changes, i.e, balance_pgdat(): > 1) call mem_cgroup_soft_limit_reclaim(), if nr_reclaimed is meet, goto finish. > 2) shrink the global LRU list, and skip the pages which belong to the cgroup > who have set a reserve_limit. if nr_reclaimed is meet, goto finish. Isn't this an overhead that would slow the whole thing down. Consider that you would need to lookup page_cgroup for every page and touch mem_cgroup to get the limit. The point of the isolation is to not touch the global reclaim path at all. > 3) shrink the cgroups who have set a reserve_limit, and leave them with only > the reserve_limit bytes they need. if nr_reclaimed is meet, goto finish. > 4) OOM > > Does it make sense? It sounds like a good thing - in that regard it is more generic than a simple flag - but I am afraid that the implementation wouldn't be that easy to preserve the performance and keep the balance between groups. But maybe it can be done without too much cost. Thanks -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx 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>