Hi, As we all know, if memcg is enabled but without any non-root memcgs, all allocated pages belong to root memcg and go through root memcg statistic routines which brings some overheads. In this pathset we try to give up accounting stats of root memcg including CACHE/RSS/SWAP/FILE_MAPPED/PGFAULT/PGMAJFAULT(First attempt can be found here: https://lkml.org/lkml/2012/12/25/103). But we need to pay special attention while showing these 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 we can fake these figures by using stats of global state and all other memcgs. Take CACHE stats for example, that is for root memcg: nr(MEM_CGROUP_STAT_CACHE) = global_page_state(NR_FILE_PAGES) - sum_of_all_memcg(MEM_CGROUP_STAT_CACHE); On a 4g memory and 4-core i5 CPU machine, we run Mel's pft test for performance numbers: nomemcg : memcg compile disabled. vanilla : memcg enabled, patch not applied. optimized: memcg enabled, with patch applied. optimized vanilla User 405.15 431.27 System 71.71 73.00 Elapsed 483.23 510.00 optimized nomemcg User 405.15 390.68 System 71.71 67.21 Elapsed 483.23 466.15 Note that elapsed time reduce considerably from 510 to 483 after pathes have been applied(about ~5%). But there is still some gap between the patched and memcg-disabled kernel, and we can also do some further works here(the left-over stats like PGPGIN/PGPGOUT). I split the patchset to several parts mainly based on their accounting entry function for the convenience of review: Sha Zhengju (6): memcg: use global stat directly for root memcg usage memcg: Don't account root memcg CACHE/RSS stats memcg: Don't account root memcg MEM_CGROUP_STAT_FILE_MAPPED stats memcg: Don't account root memcg swap stats memcg: Don't account root memcg PGFAULT/PGMAJFAULT memcg: disable memcg page stat accounting include/linux/memcontrol.h | 23 +++++++ mm/memcontrol.c | 149 +++++++++++++++++++++++++++++++++++++------- 2 files changed, 149 insertions(+), 23 deletions(-) -- 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>