From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965916AbcHDVGL (ORCPT ); Thu, 4 Aug 2016 17:06:11 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:50467 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759014AbcHDVGJ (ORCPT ); Thu, 4 Aug 2016 17:06:09 -0400 Date: Thu, 4 Aug 2016 14:06:07 -0700 From: Andrew Morton To: Aruna Ramakrishna Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mike Kravetz , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim Subject: Re: [PATCH v2] mm/slab: Improve performance of gathering slabinfo stats Message-Id: <20160804140607.49e84fd1e24f5e03bc151538@linux-foundation.org> In-Reply-To: <1470337273-6700-1-git-send-email-aruna.ramakrishna@oracle.com> References: <1470337273-6700-1-git-send-email-aruna.ramakrishna@oracle.com> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.