From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f41.google.com (mail-wm0-f41.google.com [74.125.82.41]) by kanga.kvack.org (Postfix) with ESMTP id 50CBB6B0009 for ; Fri, 29 Jan 2016 10:21:34 -0500 (EST) Received: by mail-wm0-f41.google.com with SMTP id 128so57259546wmz.1 for ; Fri, 29 Jan 2016 07:21:34 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id qr6si22711056wjc.206.2016.01.29.07.21.32 for (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 29 Jan 2016 07:21:33 -0800 (PST) Subject: Re: [PATCH 16/16] mm/slab: introduce new slab management type, OBJFREELIST_SLAB References: <1452749069-15334-1-git-send-email-iamjoonsoo.kim@lge.com> <1452749069-15334-17-git-send-email-iamjoonsoo.kim@lge.com> <56A8C788.9000004@suse.cz> <20160128045128.GC14467@js1304-P5Q-DELUXE> From: Vlastimil Babka Message-ID: <56AB837A.5090702@suse.cz> Date: Fri, 29 Jan 2016 16:21:30 +0100 MIME-Version: 1.0 In-Reply-To: <20160128045128.GC14467@js1304-P5Q-DELUXE> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Jesper Dangaard Brouer , linux-mm@kvack.org, linux-kernel@vger.kernel.org On 01/28/2016 05:51 AM, Joonsoo Kim wrote: > On Wed, Jan 27, 2016 at 02:35:04PM +0100, Vlastimil Babka wrote: >> On 01/14/2016 06:24 AM, Joonsoo Kim wrote: >> > 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 patch doesn't include it. >> >> Can you elaborate? Do we actually need an extendable linked array? Why not just >> store the pointer to the next free object into the object, NULL for the last >> one? I.e. a singly-linked list. We should never need to actually traverse it? > > As Christoph explained, it's the way SLUB manages freed objects. In SLAB > case, it doesn't want to touch object itself. It's one of main difference > between SLAB and SLUB. These objects are cache-cold now so touching object itself > could cause more cache footprint. Hm I see. Although I wouldn't bet on whether the now-freed object is more or less cold than the freelist array itself (regardless of its placement) :) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org