From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756419Ab2IYNRU (ORCPT ); Tue, 25 Sep 2012 09:17:20 -0400 Received: from mail.skyhub.de ([78.46.96.112]:40495 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756379Ab2IYNRR (ORCPT ); Tue, 25 Sep 2012 09:17:17 -0400 Date: Tue, 25 Sep 2012 15:17:36 +0200 From: Borislav Petkov To: Peter Zijlstra Cc: Linus Torvalds , Mike Galbraith , Mel Gorman , Nikolay Ulyanitsky , linux-kernel@vger.kernel.org, Andreas Herrmann , Andrew Morton , Thomas Gleixner , Ingo Molnar , Suresh Siddha Subject: Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to 3.6-rc5 on AMD chipsets - bisected Message-ID: <20120925131736.GA30652@x1.osrc.amd.com> Mail-Followup-To: Borislav Petkov , Peter Zijlstra , Linus Torvalds , Mike Galbraith , Mel Gorman , Nikolay Ulyanitsky , linux-kernel@vger.kernel.org, Andreas Herrmann , Andrew Morton , Thomas Gleixner , Ingo Molnar , Suresh Siddha References: <1348503163.11847.97.camel@twins> <1348505683.11847.111.camel@twins> <1348511193.6951.44.camel@marge.simpson.net> <20120924192056.GB4082@liondog.tnic> <1348538258.7100.23.camel@marge.simpson.net> <1348574286.3881.40.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1348574286.3881.40.camel@twins> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 25, 2012 at 01:58:06PM +0200, Peter Zijlstra wrote: > On Mon, 2012-09-24 at 19:11 -0700, Linus Torvalds wrote: > > In the not-so-distant past, we had the intel "Dunnington" Xeon, which > > was iirc basically three Core 2 duo's bolted together (ie three > > clusters of two cores sharing L2, and a fully shared L3). So that was > > a true multi-core with fairly big shared L2, and it really would be > > sad to not use the second core aggressively. > > Ah indeed. My Core2Quad didn't have an L3 afaik (its sitting around > without a PSU atm so checking gets a little hard) so the LLC level was > the L2 and all worked out right (it also not having SMT helped of > course). > > But if there was a Xeon chip that did add a package L3 then yes, all > this would become more interesting still. We'd need to extend the > scheduler topology a bit as well, I don't think it can currently handle > this well. > > So I guess we get to do some work for steamroller. Right, but before that we can still do some experimenting on Bulldozer - we have the shared 2M L2 there too and it would be nice to improve select_idle_sibling there. For example, I did some measurements a couple of days ago on Bulldozer of tbench with and without select_idle_sibling: tbench runs single-socket OR-B (box has 8 cores, 4 CUs) (tbench_srv localhost), tbench default settings as in debian testing # clients 1 2 4 8 12 16 3.6-rc6+tip/auto-latest 115.91 238.571 469.606 1865.77 1863.08 1851.46 3.6-rc6+tip/auto-latest-kill select_idle_sibling(): 354.619 534.714 900.069 1969.35 1955.91 1940.84 3.6-rc6+tip/auto-latest ----------------------- Throughput 115.91 MB/sec 1 clients 1 procs max_latency=0.296 ms Throughput 238.571 MB/sec 2 clients 2 procs max_latency=1.296 ms Throughput 469.606 MB/sec 4 clients 4 procs max_latency=0.340 ms Throughput 1865.77 MB/sec 8 clients 8 procs max_latency=3.393 ms Throughput 1863.08 MB/sec 12 clients 12 procs max_latency=0.322 ms Throughput 1851.46 MB/sec 16 clients 16 procs max_latency=2.059 ms 3.6-rc6+tip/auto-latest-kill select_idle_sibling() -------------------------------------------------- Throughput 354.619 MB/sec 1 clients 1 procs max_latency=0.321 ms Throughput 534.714 MB/sec 2 clients 2 procs max_latency=2.651 ms Throughput 900.069 MB/sec 4 clients 4 procs max_latency=10.823 ms Throughput 1969.35 MB/sec 8 clients 8 procs max_latency=1.630 ms Throughput 1955.91 MB/sec 12 clients 12 procs max_latency=3.236 ms Throughput 1940.84 MB/sec 16 clients 16 procs max_latency=0.314 ms So improving this select_idle_sibling thing wouldn't be such a bad thing. Btw, I'll run your patch at http://marc.info/?l=linux-kernel&m=134850571330618 with the same benchmark to see what it brings. Thanks. -- Regards/Gruss, Boris.