(2012/12/26 2:27), Sha Zhengju wrote: > From: Sha Zhengju <handai.szj@xxxxxxxxxx> > > If memcg is enabled and no non-root memcg exists, all allocated pages > belongs to root_mem_cgroup and go through root memcg statistics routines > which brings some overheads. So for the sake of performance, we can give > up accounting stats of root memcg for MEM_CGROUP_STAT_FILE_MAPPED/FILE_DIRTY > /WRITEBACK and instead we pay special attention while showing root > memcg numbers in memcg_stat_show(): as we don't account root memcg stats > anymore, the root_mem_cgroup->stat numbers are actually 0. But because of > hierachy, figures of root_mem_cgroup may just represent numbers of pages > used by its own tasks(not belonging to any other child cgroup). So here we > fake these root numbers by using stats of global state and all other memcg. > That is for root memcg: > nr(MEM_CGROUP_STAT_FILE_MAPPED) = global_page_state(NR_FILE_MAPPED) - > sum_of_all_memcg(MEM_CGROUP_STAT_FILE_MAPPED); > Dirty/Writeback pages accounting are in the similar way. > > Signed-off-by: Sha Zhengju <handai.szj@xxxxxxxxxx> isn't it better to use mem_cgroup_is_root() call rather than direct comparison (memcg == root_mem_cgroup) ? Anyway, Ack to this approach. Thanks, -Kame -- 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>