Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756210AbXIEG6T (ORCPT ); Wed, 5 Sep 2007 02:58:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755051AbXIEG6L (ORCPT ); Wed, 5 Sep 2007 02:58:11 -0400 Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:51488 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754823AbXIEG6K (ORCPT ); Wed, 5 Sep 2007 02:58:10 -0400 Date: Tue, 4 Sep 2007 23:58:09 -0700 (PDT) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: "Zhang, Yanmin" cc: LKML , mingo@elte.hu Subject: Re: tbench regression - Why process scheduler has impact on tbench and why small per-cpu slab (SLUB) cache creates the scenario? In-Reply-To: <1188969725.26438.46.camel@ymzhang> Message-ID: References: <1188953218.26438.34.camel@ymzhang> <1188969725.26438.46.camel@ymzhang> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1879 Lines: 44 On Wed, 5 Sep 2007, Zhang, Yanmin wrote: > On Tue, 2007-09-04 at 20:59 -0700, Christoph Lameter wrote: > > On Wed, 5 Sep 2007, Zhang, Yanmin wrote: > > > > > 8) kmalloc-4096 order is 1 which means one slab consists of 2 objects. So a > > > > You can change that by booting with slub_max_order=0. Then we can also use > > the per cpu queues to get these order 0 objects which may speed up the > > allocations because we do not have to take zone locks on slab allocation. > > > > Note also that Andrew's tree has a page allocator pass through for SLUB > > for 4k kmallocs bypassing slab completely. That may also address the > > issue. > > > > If you want SLUB to handle more objects in the 4k kmalloc cache > > without going to the page allocator then you can boot f.e. with > > > > slub_max_order=3 slub_min_objects=8 > I tried this approach. The testing result showed 2.6.23-rc4 is about > 2.5% better than 2.6.22. It really resovles the issue. > > However, the approach treats the slabs in the same policy. Could we > implement a per-slab specific approach like direct b)? I am not sure what you mean by same policy. Same configuration for all slabs? > > Try the ways to address the issue that I mentioned above. > I really appreciate your kind comments! Would it be possible to try the two other approaches that I suggested? I think both of those may also solve the issue. Try booting with slab_max_order=0 and see what effect it has. The queues of the page allocator can be much larger than what slab has for 4k pages. There is really not much of a point in using a slab allocator for page sized allocations. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/