Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751736AbaAMNWD (ORCPT ); Mon, 13 Jan 2014 08:22:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:19082 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751280AbaAMNWB (ORCPT ); Mon, 13 Jan 2014 08:22:01 -0500 Date: Mon, 13 Jan 2014 14:23:30 +0100 From: Alexander Gordeev To: Andi Kleen Cc: linux-kernel@vger.kernel.org, Arnaldo Carvalho de Melo , Jiri Olsa , Ingo Molnar , Frederic Weisbecker , Peter Zijlstra , Andi Kleen Subject: Re: [PATCH RFC v2 0/4] perf: IRQ-bound performance events Message-ID: <20140113132330.GA2833@dhcp-26-207.brq.redhat.com> References: <20140105175949.GC27909@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140105175949.GC27909@tassilo.jf.intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jan 05, 2014 at 09:59:49AM -0800, Andi Kleen wrote: > > This is version 2 of RFC "perf: IRQ-bound performance events". That is an > > introduction of IRQ-bound performance events - ones that only count in a > > context of a hardware interrupt handler. Ingo suggested to extend this > > functionality to softirq and threaded handlers as well: > > Did you measure the overhead in workloads that do a lot of interrupts? > I assume two WRMSR could be a significant part of the cost of small interrupts. No, that would be the next step. I hoped first to ensure the way I am intruding into the current perf design is correct. > For counting at least it would be likely a lot cheaper to just RDPMC > and subtract manually. Sigh, that seems as quite a rework for Intel PMU. > The cache miss example below is certainly misleading, as cache misses > by interrupts are often a "debt", that is they are forced on whoever > is interrupted. I don't think that is a good use of this. May be useless rather than misleading? :) Actually, cache and power use are exactly the data I thought are useful if one wants to check the dependency from the interrupt affinity mask. There was some discussion on this topic some year ago: On Mon, May 21, 2012 at 08:36:09AM -0700, Linus Torvalds wrote: "So it may well make perfect sense to allow a mask of CPU's for interrupt delivery, but just make sure that the mask all points to CPU's on the same socket. That would give the hardware some leeway in choosing the actual core - it's very possible that hardware could avoid cores that are running with irq's disabled (possibly improving latecy) or even more likely - avoid cores that are in deeper powersaving modes." So this RFC is kind of follow-up to come up with necessary tooling. > I guess it can be useful for cycles. > > -Andi Thanks, Andi! -- Regards, Alexander Gordeev agordeev@redhat.com -- 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/