From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759039AbcHDVtn (ORCPT ); Thu, 4 Aug 2016 17:49:43 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:21456 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758987AbcHDVtm (ORCPT ); Thu, 4 Aug 2016 17:49:42 -0400 Subject: Re: [PATCH v2] mm/slab: Improve performance of gathering slabinfo stats To: Andrew Morton References: <1470337273-6700-1-git-send-email-aruna.ramakrishna@oracle.com> <20160804140607.49e84fd1e24f5e03bc151538@linux-foundation.org> Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mike Kravetz , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim From: Aruna Ramakrishna Message-ID: Date: Thu, 4 Aug 2016 14:49:29 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2 MIME-Version: 1.0 In-Reply-To: <20160804140607.49e84fd1e24f5e03bc151538@linux-foundation.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/04/2016 02:06 PM, Andrew Morton wrote: > On Thu, 4 Aug 2016 12:01:13 -0700 Aruna Ramakrishna wrote: > >> On large systems, when some slab caches grow to millions of objects (and >> many gigabytes), running 'cat /proc/slabinfo' can take up to 1-2 seconds. >> During this time, interrupts are disabled while walking the slab lists >> (slabs_full, slabs_partial, and slabs_free) for each node, and this >> sometimes causes timeouts in other drivers (for instance, Infiniband). >> >> This patch optimizes 'cat /proc/slabinfo' by maintaining a counter for >> total number of allocated slabs per node, per cache. This counter is >> updated when a slab is created or destroyed. This enables us to skip >> traversing the slabs_full list while gathering slabinfo statistics, and >> since slabs_full tends to be the biggest list when the cache is large, it >> results in a dramatic performance improvement. Getting slabinfo statistics >> now only requires walking the slabs_free and slabs_partial lists, and >> those lists are usually much smaller than slabs_full. We tested this after >> growing the dentry cache to 70GB, and the performance improved from 2s to >> 5ms. > > I assume this is tested on both slab and slub? > > It isn't the smallest of patches but given the seriousness of the > problem I think I'll tag it for -stable backporting. > This was only sanity-checked on slub. The performance tests were only run on slab. Thanks, Aruna