From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751684Ab0ILFdL (ORCPT ); Sun, 12 Sep 2010 01:33:11 -0400 Received: from mx4.orcon.net.nz ([219.88.242.54]:57873 "EHLO mx4.orcon.net.nz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751380Ab0ILFdJ (ORCPT ); Sun, 12 Sep 2010 01:33:09 -0400 Message-ID: <4C8C6611.20206@orcon.net.nz> Date: Sun, 12 Sep 2010 17:33:05 +1200 From: Michael Cree User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.11) Gecko/20100805 Icedove/3.0.6 MIME-Version: 1.0 To: Peter Zijlstra CC: mingo@redhat.com, dengcheng.zhu@gmail.com, yanmin_zhang@linux.intel.com, gorcunov@gmail.com, fweisbec@gmail.com, robert.richter@amd.com, ming.m.lin@intel.com, tglx@linutronix.de, hpa@zytor.com, paulus@samba.org, linux-kernel@vger.kernel.org, eranian@googlemail.com, will.deacon@arm.com, lethal@linux-sh.org, davem@davemloft.net, mingo@elte.hu, linux-alpha@vger.kernel.org Subject: Re: [tip:perf/core] perf: Rework the PMU methods References:

<4C8B3AD3.5050309@orcon.net.nz> <1284198035.2251.29.camel@laptop> In-Reply-To: <1284198035.2251.29.camel@laptop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-DSPAM-Check: by mx4.orcon.net.nz on Sun, 12 Sep 2010 17:33:06 +1200 X-DSPAM-Result: Innocent X-DSPAM-Processed: Sun Sep 12 17:33:07 2010 X-DSPAM-Confidence: 0.7618 X-DSPAM-Probability: 0.0000 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/09/10 21:40, Peter Zijlstra wrote: > On Sat, 2010-09-11 at 20:16 +1200, Michael Cree wrote: >> On 10/09/10 07:50, tip-bot for Peter Zijlstra wrote: >>> Commit-ID: a4eaf7f14675cb512d69f0c928055e73d0c6d252 >>> Gitweb: http://git.kernel.org/tip/a4eaf7f14675cb512d69f0c928055e73d0c6d252 >>> Author: Peter Zijlstra >>> AuthorDate: Wed, 16 Jun 2010 14:37:10 +0200 >>> Committer: Ingo Molnar >>> CommitDate: Thu, 9 Sep 2010 20:46:30 +0200 >>> >>> perf: Rework the PMU methods >>> >>> Replace pmu::{enable,disable,start,stop,unthrottle} with >>> pmu::{add,del,start,stop}, all of which take a flags argument. >> >> Regarding the new function alpha_pmu_stop() in >> arch/alpha/kernel/perf_event.c: >> > Could you provide a patch that makes ALPHA work again, or would you like > me to take another stab at it? Yes, done. I also took the liberty to fix an undefined variable and multiple defined variable errors that were exposed by compilation. Will reply to this with the patch. I've also tested it on a UP alpha. It worked well for a little while but after running 'perf top' for a number of seconds I got the following warning: [ 287.952977] WARNING: at arch/alpha/kernel/perf_event.c:546 alpha_pmu_start+0xd0/0x120() [ 287.952977] Modules linked in: radeon ttm drm_kms_helper hwmon cfbcopyarea cfbimgblt cfbfillrect parport_pc parport nfsd exportfs nfs lockd sunrpc ipv6 loop snd_hda_codec_atihdmi snd_hda_intel snd_hda_codec snd_pcm snd_seq snd_timer snd_seq_device ftdi_sio sg usbserial sr_mod snd cdrom r8169 ohci1394 soundcore ohci_hcd ehci_hcd ieee1394 mii snd_page_alloc ata_generic pcspkr tulip evdev usbcore pata_cypress [ 287.952977] fffffc000078fb80 fffffc00007961c8 fffffc000031dbb0 fffffc002780f400 [ 287.952977] 0000000000000000 0000000000000400 00000000000ee6b3 0000000000000000 [ 287.952977] fffffc000036cf28 fffffc002780f400 fffffc003f006240 fffffc003f343538 [ 287.952977] fffffc000036d124 0000000000000001 fffffc003f006200 0000000000000000 [ 287.952977] fffffc003f0062c8 0000000000000000 fffffc002780f410 fffffc003f0062c8 [ 287.952977] fffffc000034d118 fffffc003f0062c8 fffffc0000795b28 fffffc0000795b40 [ 287.952977] Trace: [ 287.952977] [] alpha_pmu_start+0xd0/0x120 [ 287.952977] [] perf_ctx_adjust_freq+0x138/0x150 [ 287.952977] [] perf_event_context_tick+0x1e4/0x210 [ 287.952977] [] hrtimer_run_queues+0x1b8/0x2f0 [ 287.952977] [] run_local_timers+0x18/0x40 [ 287.952977] [] update_process_times+0x3c/0xb0 [ 287.952977] [] timer_interrupt+0x9c/0x100 [ 287.952977] [] handle_IRQ_event+0x70/0x1a0 [ 287.952977] [] __do_IRQ+0xc8/0x160 [ 287.952977] [] handle_irq+0x54/0xb0 [ 287.952977] [] do_entInt+0xc4/0x1e0 [ 287.952977] [] ret_from_sys_call+0x0/0x10 [ 287.952977] [] file_free_rcu+0x54/0x70 [ 287.952977] [] estimate_accuracy+0xdc/0x120 [ 287.952977] [] cpu_idle+0x48/0x60 [ 287.952977] [] perf_event_task_sched_in+0x0/0x60 [ 287.952977] [] cpu_idle+0x30/0x60 [ 287.952977] [] rest_init+0xb0/0xd0 [ 287.952977] [] _stext+0x1c/0x20 [ 287.952977] [ 287.952977] ---[ end trace 6f10adce9e4129fa ]--- which is from the line in alpha_pmu_start() that checks that PERF_HES_STOPPED is set. I see that the backtrace is from the Alpha timer_interrupt() code which goes something like this: [do some stuff updating timer deltas then...] #ifndef CONFIG_SMP while (nticks--) update_process_times(user_mode(get_irq_regs())); #endif if (test_perf_event_pending()) { clear_perf_event_pending(); perf_event_do_pending(); } return IRQ_HANDLED; } When I added the code for handle pending events to the timer interrupt I hadn't realised that update_process_times() could call back into the perf code. I'm speculating here, but could it be that there is pending work to stop the HW counter, but the call to re-start it is beating the call to stop it? Cheers Michael.