On Mon 12-09-11 12:57:23, Johannes Weiner wrote: > root_mem_cgroup, lacking a configurable limit, was never subject to > limit reclaim, so the pages charged to it could be kept off its LRU > lists. They would be found on the global per-zone LRU lists upon > physical memory pressure and it made sense to avoid uselessly linking > them to both lists. > > The global per-zone LRU lists are about to go away on memcg-enabled > kernels, with all pages being exclusively linked to their respective > per-memcg LRU lists. As a result, pages of the root_mem_cgroup must > also be linked to its LRU lists again. Nevertheless we still do not charge them so this should be mentioned here? > > The overhead is temporary until the double-LRU scheme is going away > completely. > > Signed-off-by: Johannes Weiner <jweiner@xxxxxxxxxx> Reviewed-by: Michal Hocko <mhocko@xxxxxxx> > --- > mm/memcontrol.c | 12 ++---------- > 1 files changed, 2 insertions(+), 10 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 413e1f8..518f640 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -956,8 +956,6 @@ void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru) > mz = page_cgroup_zoneinfo(pc->mem_cgroup, page); > /* huge page split is done under lru_lock. so, we have no races. */ > MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page); > - if (mem_cgroup_is_root(pc->mem_cgroup)) > - return; > VM_BUG_ON(list_empty(&pc->lru)); > list_del_init(&pc->lru); > } > @@ -982,13 +980,11 @@ void mem_cgroup_rotate_reclaimable_page(struct page *page) > return; > > pc = lookup_page_cgroup(page); > - /* unused or root page is not rotated. */ > + /* unused page is not rotated. */ > if (!PageCgroupUsed(pc)) > return; > /* Ensure pc->mem_cgroup is visible after reading PCG_USED. */ > smp_rmb(); > - if (mem_cgroup_is_root(pc->mem_cgroup)) > - return; > mz = page_cgroup_zoneinfo(pc->mem_cgroup, page); > list_move_tail(&pc->lru, &mz->lists[lru]); > } > @@ -1002,13 +998,11 @@ void mem_cgroup_rotate_lru_list(struct page *page, enum lru_list lru) > return; > > pc = lookup_page_cgroup(page); > - /* unused or root page is not rotated. */ > + /* unused page is not rotated. */ > if (!PageCgroupUsed(pc)) > return; > /* Ensure pc->mem_cgroup is visible after reading PCG_USED. */ > smp_rmb(); > - if (mem_cgroup_is_root(pc->mem_cgroup)) > - return; > mz = page_cgroup_zoneinfo(pc->mem_cgroup, page); > list_move(&pc->lru, &mz->lists[lru]); > } > @@ -1040,8 +1034,6 @@ void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru) > /* huge page split is done under lru_lock. so, we have no races. */ > MEM_CGROUP_ZSTAT(mz, lru) += 1 << compound_order(page); > SetPageCgroupAcctLRU(pc); > - if (mem_cgroup_is_root(pc->mem_cgroup)) > - return; > list_add(&pc->lru, &mz->lists[lru]); > } > > -- > 1.7.6 > > -- > 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/ . > Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- 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@xxxxxxxxx. 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>