From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f42.google.com (mail-pa0-f42.google.com [209.85.220.42]) by kanga.kvack.org (Postfix) with ESMTP id 526D56B0038 for ; Tue, 17 Jun 2014 20:27:37 -0400 (EDT) Received: by mail-pa0-f42.google.com with SMTP id lj1so101185pab.1 for ; Tue, 17 Jun 2014 17:27:37 -0700 (PDT) Received: from lgemrelse7q.lge.com (LGEMRELSE7Q.lge.com. [156.147.1.151]) by mx.google.com with ESMTP id ff3si219450pbd.167.2014.06.17.17.27.35 for ; Tue, 17 Jun 2014 17:27:36 -0700 (PDT) Date: Wed, 18 Jun 2014 09:31:52 +0900 From: Joonsoo Kim Subject: Re: [PATCH] slab: fix oops when reading /proc/slab_allocators Message-ID: <20140618003152.GA13917@js1304-P5Q-DELUXE> References: <1402967392-7003-1-git-send-email-iamjoonsoo.kim@lge.com> <20140617072933.GA26418@esperanza> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140617072933.GA26418@esperanza> Sender: owner-linux-mm@kvack.org List-ID: To: Vladimir Davydov Cc: Andrew Morton , Pekka Enberg , Christoph Lameter , David Rientjes , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org On Tue, Jun 17, 2014 at 11:29:33AM +0400, Vladimir Davydov wrote: > Hi, > > On Tue, Jun 17, 2014 at 10:09:52AM +0900, Joonsoo Kim wrote: > [...] > > To fix the problem, I introduces object status buffer on each slab. > > With this, we can track object status precisely, so slab leak detector > > would not access active object and no kernel oops would occur. > > Memory overhead caused by this fix is only imposed to > > CONFIG_DEBUG_SLAB_LEAK which is mainly used for debugging, so memory > > overhead isn't big problem. > [...] > > > > +static size_t calculate_freelist_size(int nr_objs, size_t align) > > +{ > > + size_t freelist_size; > > + > > + freelist_size = nr_objs * sizeof(freelist_idx_t); > > + if (IS_ENABLED(CONFIG_DEBUG_SLAB_LEAK)) > > + freelist_size += nr_objs * sizeof(char); > > + > > + if (align) > > + freelist_size = ALIGN(freelist_size, align); > > + > > + return freelist_size; > > +} > > + > > static int calculate_nr_objs(size_t slab_size, size_t buffer_size, > > size_t idx_size, size_t align) > > { > > int nr_objs; > > + size_t remained_size; > > size_t freelist_size; > > + int extra_space = 0; > > > > + if (IS_ENABLED(CONFIG_DEBUG_SLAB_LEAK)) > > + extra_space = sizeof(char); > > /* > > * Ignore padding for the initial guess. The padding > > * is at most @align-1 bytes, and @buffer_size is at > > @@ -590,14 +641,15 @@ static int calculate_nr_objs(size_t slab_size, size_t buffer_size, > > * into the memory allocation when taking the padding > > * into account. > > */ > > - nr_objs = slab_size / (buffer_size + idx_size); > > + nr_objs = slab_size / (buffer_size + idx_size + extra_space); > > There is one more function that wants to know how much space per object > is spent for management. It's calculate_slab_order(): > > if (flags & CFLGS_OFF_SLAB) { > /* > * Max number of objs-per-slab for caches which > * use off-slab slabs. Needed to avoid a possible > * looping condition in cache_grow(). > */ > offslab_limit = size; > offslab_limit /= sizeof(freelist_idx_t); > > if (num > offslab_limit) > break; > } > > May be, we should update it too? Hello, Vladimir. Yes, you are right! I sent v2 with this update. :) Thanks. -- 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