From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932849Ab0I1Aas (ORCPT ); Mon, 27 Sep 2010 20:30:48 -0400 Received: from smtp-out.google.com ([74.125.121.35]:63241 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755983Ab0I1AaU (ORCPT ); Mon, 27 Sep 2010 20:30:20 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=from:to:cc:subject:date:message-id:x-mailer; b=wliCTS+Xi8oFfaWy4m8NA694ieqScaqgmfqY+H8X9pqZhO/Ta/ONPad8rLAroh2HN TwiTik92hccXjYg1gyUng== From: Nikhil Rao To: Ingo Molnar , Peter Zijlstra , Mike Galbraith Cc: Venkatesh Pallipadi , linux-kernel@vger.kernel.org, Nikhil Rao Subject: [PATCH 0/3][RFC] Improve load balancing when tasks have large weight differential Date: Mon, 27 Sep 2010 17:29:55 -0700 Message-Id: <1285633798-26886-1-git-send-email-ncrao@google.com> X-Mailer: git-send-email 1.7.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, I have attached a series of patches that improve load balancing when there is a large weight differential between tasks. These patches are based off the feedback Peter Zijlstra gave in an earlier post (see http://thread.gmane.org/gmane.linux.kernel/1015966). They can be applied to v2.6.36-rc5 or -tip without conflicts. Tested with the following setup. - Test machine is a 16 cpu box (quad-socket, quad-core). - Baseline is v2.6.36-rc5 kernel We spawn 16 SCHED_IDLE soaker threads and one SCHED_NORMAL task. On the baseline kernel, the machine has ~18% idle time. With these patches applied on top of baseline, idle time drops to 0%. v2.6.36-rc5 04:58:46 PM CPU %user %nice %sys %iowait %irq %soft %steal %idle intr/s 04:58:47 PM all 81.47 0.00 0.25 0.00 0.00 0.00 0.00 18.28 13796.00 04:58:48 PM all 81.20 0.00 0.25 0.00 0.00 0.00 0.00 18.55 13816.00 04:58:49 PM all 80.93 0.19 0.25 0.00 0.00 0.06 0.00 18.57 13965.00 04:58:50 PM all 81.40 0.00 0.25 0.00 0.00 0.00 0.00 18.35 13837.37 04:58:51 PM all 81.19 0.00 0.31 0.00 0.00 0.00 0.00 18.50 13592.08 04:58:52 PM all 81.25 0.00 0.25 0.00 0.00 0.00 0.00 18.50 13721.00 04:58:53 PM all 81.19 0.00 0.25 0.00 0.00 0.00 0.00 18.56 13764.00 04:58:54 PM all 81.25 0.00 0.25 0.00 0.00 0.00 0.00 18.50 13841.41 04:58:55 PM all 80.30 0.00 1.19 0.00 0.00 0.00 0.00 18.51 14989.11 04:58:56 PM all 80.77 0.00 0.50 0.00 0.00 0.00 0.00 18.73 13964.65 Average: all 81.09 0.02 0.37 0.00 0.00 0.01 0.00 18.51 13929.53 v2.6.36-rc5 + patches 05:00:06 PM CPU %user %nice %sys %iowait %irq %soft %steal %idle intr/s 05:00:07 PM all 99.94 0.00 0.06 0.00 0.00 0.00 0.00 0.00 16364.00 05:00:08 PM all 99.81 0.06 0.12 0.00 0.00 0.00 0.00 0.00 16348.00 05:00:09 PM all 99.94 0.00 0.06 0.00 0.00 0.00 0.00 0.00 16330.00 05:00:10 PM all 99.94 0.00 0.06 0.00 0.00 0.00 0.00 0.00 16317.00 05:00:11 PM all 99.88 0.06 0.06 0.00 0.00 0.00 0.00 0.00 16327.00 05:00:12 PM all 99.94 0.00 0.06 0.00 0.00 0.00 0.00 0.00 16323.00 05:00:13 PM all 99.88 0.00 0.12 0.00 0.00 0.00 0.00 0.00 16323.00 05:00:14 PM all 99.94 0.00 0.06 0.00 0.00 0.00 0.00 0.00 16321.00 05:00:15 PM all 99.63 0.06 0.25 0.00 0.00 0.06 0.00 0.00 16354.00 05:00:16 PM all 99.62 0.00 0.38 0.00 0.00 0.00 0.00 0.00 19059.60 Average: all 99.85 0.02 0.13 0.00 0.00 0.01 0.00 0.00 16604.20 Comments, feedback welcome. -Thanks, Nikhil Nikhil Rao (3): sched: set group_imb only a task can be pulled from the busiest cpu sched: drop group_capacity to 1 only if remote group has no running tasks sched: do not consider SCHED_IDLE tasks to be cache hot kernel/sched.c | 3 +++ kernel/sched_fair.c | 12 ++++++++---- 2 files changed, 11 insertions(+), 4 deletions(-)