From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755141AbaE1Tza (ORCPT ); Wed, 28 May 2014 15:55:30 -0400 Received: from mga02.intel.com ([134.134.136.20]:26993 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751487AbaE1Tz3 (ORCPT ); Wed, 28 May 2014 15:55:29 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.98,929,1392192000"; d="scan'208";a="519232582" Date: Wed, 28 May 2014 12:55:28 -0700 From: Andi Kleen To: Stephane Eranian Cc: LKML , Peter Zijlstra , "mingo@elte.hu" , Dave Hansen , "Yan, Zheng" Subject: Re: [RFC] perf/x86: PMU IRQ handler issues Message-ID: <20140528195528.GQ29957@tassilo.jf.intel.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Another explanation is that because we ACK the NMI early, we leave the > door open to other interrupts, incl. NIC, and we are interrupting the execution PMI executes with interrupts off. > of the PMU IRQ handler, yet that detour is measured in the PMU handler > latency, causing more throttling than needed. Is that a plausible scenario too? > And if so, I think we need to narrow the window for timing errors, by > acking late > on all processors and not just HSW. If you think there's a concrete problem please show an ftrace. -Andi -- ak@linux.intel.com -- Speaking for myself only