Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934072Ab1EWUEs (ORCPT ); Mon, 23 May 2011 16:04:48 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:41650 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933224Ab1EWUEo (ORCPT ); Mon, 23 May 2011 16:04:44 -0400 Message-ID: <4DDABDC4.1010800@us.ibm.com> Date: Mon, 23 May 2011 15:04:20 -0500 From: Maynard Johnson User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.17) Gecko/20110414 Thunderbird/3.1.10 MIME-Version: 1.0 To: Eric B Munson CC: benh@kernel.crashing.org, robert.richter@amd.com, oprofile-list@lists.sf.net, paulus@samba.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] oprofile, powerpc: Handle events that raise an exception without overflowing References: <1306160560-5309-1-git-send-email-emunson@mgebm.net> <20110523193736.GA2997@mgebm.net> In-Reply-To: <20110523193736.GA2997@mgebm.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3005 Lines: 82 Eric B Munson wrote: > On Mon, 23 May 2011, Eric B Munson wrote: > >> Commit 0837e3242c73566fc1c0196b4ec61779c25ffc93 fixes a situation on POWER7 >> where events can roll back if a specualtive event doesn't actually complete. >> This can raise a performance monitor exception. We need to catch this to ensure >> that we reset the PMC. In all cases the PMC will be less than 256 cycles from >> overflow. >> >> This patch lifts Anton's fix for the problem in perf and applies it to oprofile >> as well. >> >> Signed-off-by: Eric B Munson >> Cc: # as far back as it applies cleanly > > I'd like to get this patch into mainline this merge window if at all possible. Ack. I've been able to create a system hang profiling with speculative events on POWER7. This patch fixes that problem. -Maynard > >> --- >> arch/powerpc/oprofile/op_model_power4.c | 24 +++++++++++++++++++++++- >> 1 files changed, 23 insertions(+), 1 deletions(-) >> >> diff --git a/arch/powerpc/oprofile/op_model_power4.c b/arch/powerpc/oprofile/op_model_power4.c >> index 8ee51a2..e6bec74 100644 >> --- a/arch/powerpc/oprofile/op_model_power4.c >> +++ b/arch/powerpc/oprofile/op_model_power4.c >> @@ -261,6 +261,28 @@ static int get_kernel(unsigned long pc, unsigned long mmcra) >> return is_kernel; >> } >> >> +static bool pmc_overflow(unsigned long val) >> +{ >> + if ((int)val < 0) >> + return true; >> + >> + /* >> + * Events on POWER7 can roll back if a speculative event doesn't >> + * eventually complete. Unfortunately in some rare cases they will >> + * raise a performance monitor exception. We need to catch this to >> + * ensure we reset the PMC. In all cases the PMC will be 256 or less >> + * cycles from overflow. >> + * >> + * We only do this if the first pass fails to find any overflowing >> + * PMCs because a user might set a period of less than 256 and we >> + * don't want to mistakenly reset them. >> + */ >> + if (__is_processor(PV_POWER7) && ((0x80000000 - val) <= 256)) >> + return true; >> + >> + return false; >> +} >> + >> static void power4_handle_interrupt(struct pt_regs *regs, >> struct op_counter_config *ctr) >> { >> @@ -281,7 +303,7 @@ static void power4_handle_interrupt(struct pt_regs *regs, >> >> for (i = 0; i < cur_cpu_spec->num_pmcs; ++i) { >> val = classic_ctr_read(i); >> - if (val < 0) { >> + if (pmc_overflow(val)) { >> if (oprofile_running && ctr[i].enabled) { >> oprofile_add_ext_sample(pc, regs, i, is_kernel); >> classic_ctr_write(i, reset_value[i]); >> -- >> 1.7.4.1 >> >> >> >> _______________________________________________ >> Linuxppc-dev mailing list >> Linuxppc-dev@lists.ozlabs.org >> https://lists.ozlabs.org/listinfo/linuxppc-dev -- 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/