Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755794AbcDLEvy (ORCPT ); Tue, 12 Apr 2016 00:51:54 -0400 Received: from mail-pa0-f47.google.com ([209.85.220.47]:35311 "EHLO mail-pa0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755705AbcDLEvw (ORCPT ); Tue, 12 Apr 2016 00:51:52 -0400 From: js1304@gmail.com X-Google-Original-From: iamjoonsoo.kim@lge.com To: Andrew Morton Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Jesper Dangaard Brouer , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim Subject: [PATCH v2 06/11] mm/slab: don't keep free slabs if free_objects exceeds free_limit Date: Tue, 12 Apr 2016 13:51:01 +0900 Message-Id: <1460436666-20462-7-git-send-email-iamjoonsoo.kim@lge.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1460436666-20462-1-git-send-email-iamjoonsoo.kim@lge.com> References: <1460436666-20462-1-git-send-email-iamjoonsoo.kim@lge.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2665 Lines: 83 From: Joonsoo Kim Currently, determination to free a slab is done whenever each freed object is put into the slab. This has a following problem. Assume free_limit = 10 and nr_free = 9. Free happens as following sequence and nr_free changes as following. free(become a free slab) free(not become a free slab) nr_free: 9 -> 10 (at first free) -> 11 (at second free) If we try to check if we can free current slab or not on each object free, we can't free any slab in this situation because current slab isn't a free slab when nr_free exceed free_limit (at second free) even if there is a free slab. However, if we check it lastly, we can free 1 free slab. This problem would cause to keep too much memory in the slab subsystem. This patch try to fix it by checking number of free object after all free work is done. If there is free slab at that time, we can free slab as much as possible so we keep free slab as minimal. v2: explain more about the problem Signed-off-by: Joonsoo Kim --- mm/slab.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/mm/slab.c b/mm/slab.c index 27cb390..6e61461 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3283,6 +3283,9 @@ static void free_block(struct kmem_cache *cachep, void **objpp, { int i; struct kmem_cache_node *n = get_node(cachep, node); + struct page *page; + + n->free_objects += nr_objects; for (i = 0; i < nr_objects; i++) { void *objp; @@ -3295,17 +3298,11 @@ static void free_block(struct kmem_cache *cachep, void **objpp, check_spinlock_acquired_node(cachep, node); slab_put_obj(cachep, page, objp); STATS_DEC_ACTIVE(cachep); - n->free_objects++; /* fixup slab chains */ - if (page->active == 0) { - if (n->free_objects > n->free_limit) { - n->free_objects -= cachep->num; - list_add_tail(&page->lru, list); - } else { - list_add(&page->lru, &n->slabs_free); - } - } else { + if (page->active == 0) + list_add(&page->lru, &n->slabs_free); + else { /* Unconditionally move a slab to the end of the * partial list on free - maximum time for the * other objects to be freed, too. @@ -3313,6 +3310,14 @@ static void free_block(struct kmem_cache *cachep, void **objpp, list_add_tail(&page->lru, &n->slabs_partial); } } + + while (n->free_objects > n->free_limit && !list_empty(&n->slabs_free)) { + n->free_objects -= cachep->num; + + page = list_last_entry(&n->slabs_free, struct page, lru); + list_del(&page->lru); + list_add(&page->lru, list); + } } static void cache_flusharray(struct kmem_cache *cachep, struct array_cache *ac) -- 1.9.1