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From:   Vlastimil Babka <vbabka@suse.cz>
To:     linux-mm@kvack.org
Cc:     Roman Gushchin <guro@fb.com>, Michal Hocko <mhocko@kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
        Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Vijayanand Jitta <vjitta@codeaurora.org>,
        Vlastimil Babka <vbabka@suse.cz>
Subject: [RFC PATCH 2/5] mm, slab: allocate off-slab freelists as reclaimable when appropriate
Date:   Thu, 24 May 2018 13:00:08 +0200
Message-Id: <20180524110011.1940-3-vbabka@suse.cz>
In-Reply-To: <20180524110011.1940-1-vbabka@suse.cz>
References: <20180524110011.1940-1-vbabka@suse.cz>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In SLAB, OFF_SLAB caches allocate management structures (currently just the
freelist) from kmalloc caches when placement in a slab page together with
objects would lead to suboptimal memory usage. For SLAB_RECLAIM_ACCOUNT caches,
we can allocate the freelists from the newly introduced reclaimable kmalloc
caches, because shrinking the OFF_SLAB cache will in general result to freeing
of the freelists as well. This should improve accounting and anti-fragmentation
a bit.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/slab.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/slab.c b/mm/slab.c
index 8d7e1f06127b..4dd7d73a1972 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2142,8 +2142,13 @@ int __kmem_cache_create(struct kmem_cache *cachep, slab_flags_t flags)
 #endif
 
 	if (OFF_SLAB(cachep)) {
+		/*
+		 * If this cache is reclaimable, allocate also freelists from
+		 * a reclaimable kmalloc cache.
+		 */
 		cachep->freelist_cache =
-			kmalloc_slab(cachep->freelist_size, 0u);
+			kmalloc_slab(cachep->freelist_size,
+				     cachep->allocflags & __GFP_RECLAIMABLE);
 	}
 
 	err = setup_cpu_cache(cachep, gfp);
-- 
2.17.0