[PATCH v6 27/31] vmscan: take at least one pass with shrinkers
From: Glauber Costa <hidden>
Date: 2013-05-12 18:13:48
Also in:
linux-fsdevel, linux-mm
Subsystem:
memory management, memory management - mglru (multi-gen lru), memory management - reclaim, the rest · Maintainers:
Andrew Morton, Johannes Weiner, Linus Torvalds
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 <redacted> CC: Dave Chinner <david@fromorbit.com> CC: Carlos Maiolino <redacted> CC: "Theodore Ts'o" <tytso@mit.edu> CC: Al Viro <viro@zeniv.linux.org.uk> --- mm/vmscan.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9c45e5c..6bac41e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c@@ -273,20 +273,33 @@ shrink_slab_one(struct shrinker *shrinker, struct shrink_control *shrinkctl, 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
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