From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: [PATCH v7 30/34] vmscan: take at least one pass with shrinkers Date: Mon, 20 May 2013 00:07:23 +0400 Message-ID: <1368994047-5997-31-git-send-email-glommer@openvz.org> References: <1368994047-5997-1-git-send-email-glommer@openvz.org> Cc: , Andrew Morton , Greg Thelen , , Michal Hocko , Johannes Weiner , , Dave Chinner , hughd@google.com, Glauber Costa , Carlos Maiolino , "Theodore Ts'o" , Al Viro To: Return-path: In-Reply-To: <1368994047-5997-1-git-send-email-glommer@openvz.org> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org In very low free kernel memory situations, it may be the case that we have less objects to free than our initial batch size. If this is the case, it is better to shrink those, and open space for the new workload then to keep them and fail the new allocations. In particular, we are concerned with the direct reclaim case for memcg. Although this same technique can be applied to other situations just as well, we will start conservative and apply it for that case, which is the one that matters the most. [ v6: only do it per memcg ] [ v5: differentiate no-scan case, don't do this for kswapd ] Signed-off-by: Glauber Costa CC: Dave Chinner CC: Carlos Maiolino CC: "Theodore Ts'o" CC: Al Viro --- mm/vmscan.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 3c67f36..2a94ef6 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -297,21 +297,34 @@ shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker, nr_pages_scanned, lru_pages, max_pass, delta, total_scan); - while (total_scan >= batch_size) { + do { long ret; + unsigned long nr_to_scan = min(batch_size, total_scan); + struct mem_cgroup *memcg = shrinkctl->target_mem_cgroup; + + /* + * Differentiate between "few objects" and "no objects" + * as returned by the count step. + */ + if (!total_scan) + break; + + if ((total_scan < batch_size) && + !(memcg && memcg_kmem_is_active(memcg))) + break; - shrinkctl->nr_to_scan = batch_size; + shrinkctl->nr_to_scan = nr_to_scan; ret = shrinker->scan_objects(shrinker, shrinkctl); if (ret == -1) break; freed += ret; - count_vm_events(SLABS_SCANNED, batch_size); - total_scan -= batch_size; + count_vm_events(SLABS_SCANNED, nr_to_scan); + total_scan -= nr_to_scan; cond_resched(); - } + } while (total_scan >= batch_size); /* * move the unused scan count back into the shrinker in a -- 1.8.1.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org