From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753295AbcBZGBh (ORCPT ); Fri, 26 Feb 2016 01:01:37 -0500 Received: from mail-pa0-f51.google.com ([209.85.220.51]:34963 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750789AbcBZGBg (ORCPT ); Fri, 26 Feb 2016 01:01:36 -0500 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 , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim Subject: [PATCH v2 01/17] mm/slab: fix stale code comment Date: Fri, 26 Feb 2016 15:01:08 +0900 Message-Id: <1456466484-3442-2-git-send-email-iamjoonsoo.kim@lge.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1456466484-3442-1-git-send-email-iamjoonsoo.kim@lge.com> References: <1456466484-3442-1-git-send-email-iamjoonsoo.kim@lge.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Joonsoo Kim This patchset implements new freed object management way, that is, OBJFREELIST_SLAB. Purpose of it is to reduce memory overhead in SLAB. SLAB needs a array to manage freed objects in a slab. If there is leftover after objects are packed into a slab, we can use it as a management array, and, in this case, there is no memory waste. But, in the other cases, we need to allocate extra memory for a management array or utilize dedicated internal memory in a slab for it. Both cases causes memory waste so it's not good. With this patchset, freed object itself can be used for a management array. So, memory waste could be reduced. Detailed idea and numbers are described in last patch's commit description. Please refer it. In fact, I tested another idea implementing OBJFREELIST_SLAB with extendable linked array through another freed object. It can remove memory waste completely but it causes more computational overhead in critical lock path and it seems that overhead outweigh benefit. So, this patchset doesn't include it. I will attach prototype just for a reference. This patch (of 16): We use freelist_idx_t type for free object management whose size would be smaller than size of unsigned int. Fix it. Acked-by: Christoph Lameter Signed-off-by: Joonsoo Kim Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Jesper Dangaard Brouer Signed-off-by: Andrew Morton --- mm/slab.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/slab.c b/mm/slab.c index b3eca03..23fc4b0 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -537,7 +537,7 @@ static void cache_estimate(unsigned long gfporder, size_t buffer_size, * on it. For the latter case, the memory allocated for a * slab is used for: * - * - One unsigned int for each object + * - One freelist_idx_t for each object * - Padding to respect alignment of @align * - @buffer_size bytes for each object * -- 1.9.1