Messages in this thread | | | From | Zhu Yanhai <> | Date | Tue, 29 Mar 2011 22:02:23 +0800 | Subject | Re: [RFC 0/3] Implementation of cgroup isolation |
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Hi,
2011/3/29 Michal Hocko <mhocko@suse.cz>: > 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.
Current almost has did such things, say the direct reclaim path: shrink_inactive_list() ->isolate_pages_global() ->isolate_lru_pages() ->mem_cgroup_del_lru(for each page it wants to isolate) and in mem_cgroup_del_lru() we have: [code] pc = lookup_page_cgroup(page); /* * Used bit is set without atomic ops but after smp_wmb(). * For making pc->mem_cgroup visible, insert smp_rmb() here. */ smp_rmb(); /* unused or root page is not rotated. */ if (!PageCgroupUsed(pc) || mem_cgroup_is_root(pc->mem_cgroup)) return; [/code] By calling mem_cgroup_is_root(pc->mem_cgroup) we already brought the struct mem_cgroup into cache. So probably things won't get worse at least.
Thanks, Zhu Yanhai
> 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 >
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