fallback_alloc is called on kmalloc if the preferred node doesn't have free or partial slabs and there's no pages on the node's free list (GFP_THISNODE allocations fail). Before invoking the reclaimer it tries to locate a free or partial slab on other allowed nodes' lists. While iterating over the preferred node's zonelist it skips those zones which hardwall cpuset check returns false for. That means that for a task bound to a specific node using cpusets fallback_alloc will always ignore free slabs on other nodes and go directly to the reclaimer, which, however, may allocate from other nodes if cpuset.mem_hardwall is unset (default). As a result, we may get lists of free slabs grow without bounds on other nodes, which is bad, because inactive slabs are only evicted by cache_reap at a very slow rate and cannot be dropped forcefully. To reproduce the issue, run a process that will walk over a directory tree with lots of files inside a cpuset bound to a node that constantly experiences memory pressure. Look at num_slabs vs active_slabs growth as reported by /proc/slabinfo. To avoid this we should use softwall cpuset check in fallback_alloc. Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Acked-by: Zefan Li <lizefan@xxxxxxxxxx> --- mm/slab.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/slab.c b/mm/slab.c index 063a91bc8826..c44c17478551 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3012,7 +3012,7 @@ retry: for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) { nid = zone_to_nid(zone); - if (cpuset_zone_allowed(zone, flags | __GFP_HARDWALL) && + if (cpuset_zone_allowed(zone, flags) && get_node(cache, nid) && get_node(cache, nid)->free_objects) { obj = ____cache_alloc_node(cache, -- 1.7.10.4 -- 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>