Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757228Ab3D2JZM (ORCPT ); Mon, 29 Apr 2013 05:25:12 -0400 Received: from mail-ee0-f50.google.com ([74.125.83.50]:54682 "EHLO mail-ee0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752471Ab3D2JZJ (ORCPT ); Mon, 29 Apr 2013 05:25:09 -0400 MIME-Version: 1.0 Date: Mon, 29 Apr 2013 11:25:07 +0200 Message-ID: Subject: lttng and full nohz From: Mats Liljegren To: linux-kernel@vger.kernel.org, Frederic Weisbecker , Mathieu Desnoyers Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 965 Lines: 21 I've been investigating why lttng destroys full nohz mode, and the root cause is that lttng uses timers for flushing trace buffers. So I'm planning on moving the timers to the ticking CPU, so that any CPU using full nohz mode can continue to do so even though they might have tracepoints. I can see that kernel/sched/core.c has the function get_nohz_timer_target() which tries to find an idle CPU to allocate for a timer that has not specified a CPU to be pinned to. My question here is: For full nohz mode, should this still be "only" an idle CPU, or should it be translated to a CPU not running in full nohz mode? I'd think this could make it a lot easier to allow applications to make full use of full nohz. /Mats -- 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/