Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752518AbbFKLlZ (ORCPT ); Thu, 11 Jun 2015 07:41:25 -0400 Received: from mail-wi0-f194.google.com ([209.85.212.194]:35651 "EHLO mail-wi0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751244AbbFKLlS (ORCPT ); Thu, 11 Jun 2015 07:41:18 -0400 Message-ID: <1434022875.4051.5.camel@gmail.com> Subject: Re: RFC: futex_wait() can DoS the tick From: Mike Galbraith To: Thomas Gleixner Cc: LKML , Peter Zijlstra , Ingo Molnar , Steven Rostedt Date: Thu, 11 Jun 2015 13:41:15 +0200 In-Reply-To: References: <1433940278.6814.66.camel@gmail.com> <1433957421.6306.28.camel@gmail.com> <1433989634.3411.15.camel@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 903 Lines: 25 On Thu, 2015-06-11 at 10:34 +0200, Thomas Gleixner wrote: > Can you try the following, please? > > Enable function tracer and hrtimer events manually. Then watch the irq > count on cpu3. If it stalls or becomes slow, then stop the trace with > > echo 0 >/sys/kernel/debug/tracing/tracing_on > > If the overhead of the function tracer hides the problem, then try just > with hrtimer, sched_switch and irq events. Yeah, function tracer hides it. After some fiddling with buffer size to be able to ever see a tick, I finally have a trace trimmed with a tick on each end, 175ms gap between them. It's still 1.5 after xz, sending off list. -Mike -- 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/