Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764454Ab3DDSVq (ORCPT ); Thu, 4 Apr 2013 14:21:46 -0400 Received: from a9-42.smtp-out.amazonses.com ([54.240.9.42]:49963 "EHLO a9-42.smtp-out.amazonses.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764368Ab3DDSVp (ORCPT ); Thu, 4 Apr 2013 14:21:45 -0400 X-Greylist: delayed 689 seconds by postgrey-1.27 at vger.kernel.org; Thu, 04 Apr 2013 14:21:45 EDT Date: Thu, 4 Apr 2013 18:10:14 +0000 From: Christoph Lameter X-X-Sender: cl@gentwo.org To: Frederic Weisbecker cc: Ingo Molnar , LKML , Andrew Morton , Chris Metcalf , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , Kevin Hilman , Li Zhong , Namhyung Kim , "Paul E. McKenney" , Paul Gortmaker , Peter Zijlstra , Steven Rostedt , Thomas Gleixner , Michal Marek Subject: Re: [RFC GIT PULL] nohz: Kconfig layout improvements In-Reply-To: <1364993190-13784-1-git-send-email-fweisbec@gmail.com> Message-ID: <0000013dd63de989-c6980852-2aac-4597-ba34-3b2efaa24c17-000000@email.amazonses.com> References: <1364993190-13784-1-git-send-email-fweisbec@gmail.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-SES-Outgoing: 2013.04.04-54.240.9.42 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1890 Lines: 56 It seems that nohz still has no effect. 3.9-rc5 + patches. Affinity of init set to 0,1 so no tasks are running on 9. The "latencytest" used here is part of my lldiag-0.15 toolkit. First test without any special kernel parameters. nohz off right? $ nice -5 taskset -c 9 latencytest CPUs: Freq=2.90Ghz Processors=32 Cores=8 cacheline_size=64 Intel(R) Xeon(R) CPU E5-2690 0 @ 2.90GHz 16775106 samples below 1000 nsec 13 involuntary context switches 1019 (0.00607411%) variances in 10.00 seconds: minimum 1.07us maximum 12.32us average 3.30us stddev 0.63us HZ=100 so the 1019 variances are likely timer interrupts. After nohz setup /proc/cmdline: BOOT_IMAGE=/vmlinuz-3.9.0-rc5+ root=/dev/mapper/vg01-root ro console=tty0 console=ttyS0,115200 idle=mwait rcu_nocb_poll rcu_nocbs=2-31 nohz_extended=2-31 $ nice -5 taskset -c 9 latencytest CPUs: Freq=2.90Ghz Processors=32 Cores=8 cacheline_size=64 Intel(R) Xeon(R) CPU E5-2690 0 @ 2.90GHz 16779362 samples below 1000 nsec 13 involuntary context switches 1037 (0.00617983%) variances in 10.00 seconds: minimum 1.00us maximum 10.61us average 3.30us stddev 0.98us If I move the RCU threads off the cpu then I get a slightly better result: $ nice -5 taskset -c 9 latencytest CPUs: Freq=2.90Ghz Processors=32 Cores=8 cacheline_size=64 Intel(R) Xeon(R) CPU E5-2690 0 @ 2.90GHz 16796039 samples below 1000 nsec 12 involuntary context switches 1020 (0.00607249%) variances in 10.00 seconds: minimum 1.00us maximum 11.58us average 2.77us stddev 0.55us Why is the tick not stopping? How do I diagnose this? (I can start patching the kernel again like last time but isnt there a better way?) -- 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/