From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754332Ab3KYMLB (ORCPT ); Mon, 25 Nov 2013 07:11:01 -0500 Received: from relay.parallels.com ([195.214.232.42]:53459 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753883Ab3KYMHw (ORCPT ); Mon, 25 Nov 2013 07:07:52 -0500 From: Vladimir Davydov To: , CC: , , , , Subject: [PATCH v11 08/15] vmscan: take at least one pass with shrinkers Date: Mon, 25 Nov 2013 16:07:41 +0400 Message-ID: <2ddb3940d9a96ba6625809a17e23ccb4e65fe29d.1385377616.git.vdavydov@parallels.com> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.30.24.145] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Glauber Costa 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. 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 36fc133..bfedcdc 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -311,20 +311,33 @@ 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 { unsigned 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 == SHRINK_STOP) 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 -- 1.7.10.4