Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753691AbZK0Cbq (ORCPT ); Thu, 26 Nov 2009 21:31:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753607AbZK0Cbp (ORCPT ); Thu, 26 Nov 2009 21:31:45 -0500 Received: from ozlabs.org ([203.10.76.45]:57776 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752415AbZK0Cbp (ORCPT ); Thu, 26 Nov 2009 21:31:45 -0500 Date: Fri, 27 Nov 2009 13:28:20 +1100 From: Anton Blanchard To: mingo@elte.hu Cc: linux-kernel@vger.kernel.org, msb@google.com, fweisbec@gmail.com Subject: PATCH: softlockup: Fix hung_task_check_count sysctl Message-ID: <20091127022820.GU32182@kryten> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1109 Lines: 30 I'm seeing spikes of up to 0.5ms in khungtaskd on a large machine. To reduce this source of jitter I tried setting hung_task_check_count to 0: # echo 0 > /proc/sys/kernel/hung_task_check_count which didn't have the intended response. Change to a post increment of max_count, so a value of 0 means check 0 tasks. Signed-off-by: Anton Blanchard --- Index: linux.trees.git/kernel/hung_task.c =================================================================== --- linux.trees.git.orig/kernel/hung_task.c 2009-11-27 13:11:46.000000000 +1100 +++ linux.trees.git/kernel/hung_task.c 2009-11-27 13:11:57.000000000 +1100 @@ -144,7 +144,7 @@ static void check_hung_uninterruptible_t rcu_read_lock(); do_each_thread(g, t) { - if (!--max_count) + if (!max_count--) goto unlock; if (!--batch_count) { batch_count = HUNG_TASK_BATCHING; -- 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/