Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756733Ab0BXLNr (ORCPT ); Wed, 24 Feb 2010 06:13:47 -0500 Received: from ozlabs.org ([203.10.76.45]:41507 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756588Ab0BXLNq (ORCPT ); Wed, 24 Feb 2010 06:13:46 -0500 From: Michael Neuling To: Peter Zijlstra cc: Joel Schopp , Ingo Molnar , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, ego@in.ibm.com, Suresh Siddha Subject: Re: [PATCHv4 2/2] powerpc: implement arch_scale_smt_power for Power7 In-reply-to: <4886.1266991633@neuling.org> References: <1264017638.5717.121.camel@jschopp-laptop> <1264017847.5717.132.camel@jschopp-laptop> <1264548495.12239.56.camel@jschopp-laptop> <1264720855.9660.22.camel@jschopp-laptop> <1264721088.10385.1.camel@jschopp-laptop> <1265403478.6089.41.camel@jschopp-laptop> <1266142340.5273.418.camel@laptop> <25851.1266445258@neuling.org> <1266499023.26719.597.camel@laptop> <14639.1266559532@neuling.org> <1266573672.1806.70.camel@laptop> <24165.1266577276@neuling.org> <23662.1266905307@neuling.org> <1266942281.11845.521.camel@laptop> <4886.1266991633@neuling.org> Comments: In-reply-to Michael Neuling message dated "Wed, 24 Feb 2010 17:07:13 +1100." X-Mailer: MH-E 8.2; nmh 1.3; GNU Emacs 23.1.1 Date: Wed, 24 Feb 2010 22:13:44 +1100 Message-ID: <11927.1267010024@neuling.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2221 Lines: 68 > > If there's less the group will normally be balanced and we fall out and > > end up in check_asym_packing(). > > > > So what I tried doing with that loop is detect if there's a hole in the > > packing before busiest. Now that I think about it, what we need to check > > is if this_cpu (the removed cpu argument) is idle and less than busiest. > > > > So something like: > > > > static int check_asym_pacing(struct sched_domain *sd, > > struct sd_lb_stats *sds, > > int this_cpu, unsigned long *imbalance) > > { > > int busiest_cpu; > > > > if (!(sd->flags & SD_ASYM_PACKING)) > > return 0; > > > > if (!sds->busiest) > > return 0; > > > > busiest_cpu = group_first_cpu(sds->busiest); > > if (cpu_rq(this_cpu)->nr_running || this_cpu > busiest_cpu) > > return 0; > > > > *imbalance = (sds->max_load * sds->busiest->cpu_power) / > > SCHED_LOAD_SCALE; > > return 1; > > } > > > > Does that make sense? > > I think so. > > I'm seeing check_asym_packing do the right thing with the simple SMT2 > with 1 process case. It marks cpu0 as imbalanced when cpu0 is idle and > cpu1 is busy. > > Unfortunately the process doesn't seem to be get migrated down though. > Do we need to give *imbalance a higher value? So with ego help, I traced this down a bit more. In my simple test case (SMT2, t0 idle, t1 active) if f_b_g() hits our new case in check_asym_packing(), load_balance then runs f_b_q(). f_b_q() has this: if (capacity && rq->nr_running == 1 && wl > imbalance) continue; when check_asym_packing() hits, wl = 1783 and imbalance = 1024, so we continue and busiest remains NULL. load_balance then does "goto out_balanced" and it doesn't attempt to move the task. Based on this and on egos suggestion I pulled in Suresh Siddha patch from: http://lkml.org/lkml/2010/2/12/352. This fixes the problem. The process is moved down to t0. I've only tested SMT2 so far. Mikey -- 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/