mem_cgroup_should_soft_reclaim controls whether soft reclaim pass is done and it always says yes currently. Memcg iterators are clever to skip nodes that are not soft reclaimable quite efficiently but mem_cgroup_should_soft_reclaim can be more clever and do not start the soft reclaim pass at all if it knows that nothing would be scanned anyway. In order to do that, simply reuse mem_cgroup_soft_reclaim_eligible for the target group of the reclaim and allow the pass only if the whole subtree wouldn't be skipped. Changes since v1 - do not export mem_cgroup_root and teach mem_cgroup_soft_reclaim_eligible to handle NULL memcg as mem_cgroup_root Signed-off-by: Michal Hocko <mhocko@xxxxxxx> --- mm/memcontrol.c | 6 +++++- mm/vmscan.c | 4 +++- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 2a06d5a..b2e44d3 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1987,7 +1987,11 @@ enum mem_cgroup_filter_t mem_cgroup_soft_reclaim_eligible(struct mem_cgroup *memcg, struct mem_cgroup *root) { - struct mem_cgroup *parent = memcg; + struct mem_cgroup *parent; + + if (!memcg) + memcg = root_mem_cgroup; + parent = memcg; if (res_counter_soft_limit_excess(&memcg->res)) return VISIT; diff --git a/mm/vmscan.c b/mm/vmscan.c index 79d59ec..56302da 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -142,7 +142,9 @@ static bool global_reclaim(struct scan_control *sc) static bool mem_cgroup_should_soft_reclaim(struct scan_control *sc) { - return !mem_cgroup_disabled(); + struct mem_cgroup *root = sc->target_mem_cgroup; + return !mem_cgroup_disabled() && + mem_cgroup_soft_reclaim_eligible(root, root) != SKIP_TREE; } #else static bool global_reclaim(struct scan_control *sc) -- 1.8.3.1 -- 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>