On Tue 29-03-11 22:02:23, Zhu Yanhai wrote: > Hi, > > 2011/3/29 Michal Hocko <mhocko@xxxxxxx>: > > 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. But we would still have to isolate and put back a lot of pages potentially. If we do not have those pages on the list we will skip them automatically. -- 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>