From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 52B94C352A3 for ; Tue, 11 Feb 2020 12:49:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2D692246A7 for ; Tue, 11 Feb 2020 12:49:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728572AbgBKMrx (ORCPT ); Tue, 11 Feb 2020 07:47:53 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:45986 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728492AbgBKMrw (ORCPT ); Tue, 11 Feb 2020 07:47:52 -0500 Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1j1Ux7-0007Yg-K0; Tue, 11 Feb 2020 13:47:45 +0100 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id 3B8F61C2018; Tue, 11 Feb 2020 13:47:45 +0100 (CET) Date: Tue, 11 Feb 2020 12:47:44 -0000 From: "tip-bot2 for Kan Liang" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: perf/core] perf/x86/intel: Avoid unnecessary PEBS_ENABLE MSR access in PMI Cc: Kan Liang , "Peter Zijlstra (Intel)" , Ingo Molnar , x86 , LKML In-Reply-To: <20200121181338.3234-1-kan.liang@linux.intel.com> References: <20200121181338.3234-1-kan.liang@linux.intel.com> MIME-Version: 1.0 Message-ID: <158142526498.411.9050167977316432936.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the perf/core branch of tip: Commit-ID: 6c1c07b33eb093e5a2a313ece89baa596ba6135e Gitweb: https://git.kernel.org/tip/6c1c07b33eb093e5a2a313ece89baa596ba6135e Author: Kan Liang AuthorDate: Tue, 21 Jan 2020 10:13:38 -08:00 Committer: Ingo Molnar CommitterDate: Tue, 11 Feb 2020 13:23:48 +01:00 perf/x86/intel: Avoid unnecessary PEBS_ENABLE MSR access in PMI The perf PMI handler, intel_pmu_handle_irq(), currently does unnecessary MSR accesses for PEBS_ENABLE MSR in __intel_pmu_enable/disable_all() when PEBS is enabled. When entering the handler, global ctrl is explicitly disabled. All counters do not count anymore. It doesn't matter if PEBS is enabled or not in a PMI handler. Furthermore, for most cases, the cpuc->pebs_enabled is not changed in PMI. The PEBS status doesn't change. The PEBS_ENABLE MSR doesn't need to be changed either when exiting the handler. PMI throttle may change the PEBS status during PMI handler. The x86_pmu_stop() ends up in intel_pmu_pebs_disable() which can update cpuc->pebs_enabled. But the MSR_IA32_PEBS_ENABLE is not updated at the same time. Because the cpuc->enabled has been forced to 0. The patch explicitly update the MSR_IA32_PEBS_ENABLE for this case. Use ftrace to measure the duration of intel_pmu_handle_irq() on BDX. #perf record -e cycles:P -- ./tchain_edit The average duration of intel_pmu_handle_irq(): Without the patch 1.144 us With the patch 1.025 us Signed-off-by: Kan Liang Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lkml.kernel.org/r/20200121181338.3234-1-kan.liang@linux.intel.com --- arch/x86/events/intel/core.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index dff6623..332954c 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -1945,6 +1945,14 @@ static __initconst const u64 knl_hw_cache_extra_regs * intel_bts events don't coexist with intel PMU's BTS events because of * x86_add_exclusive(x86_lbr_exclusive_lbr); there's no need to keep them * disabled around intel PMU's event batching etc, only inside the PMI handler. + * + * Avoid PEBS_ENABLE MSR access in PMIs. + * The GLOBAL_CTRL has been disabled. All the counters do not count anymore. + * It doesn't matter if the PEBS is enabled or not. + * Usually, the PEBS status are not changed in PMIs. It's unnecessary to + * access PEBS_ENABLE MSR in disable_all()/enable_all(). + * However, there are some cases which may change PEBS status, e.g. PMI + * throttle. The PEBS_ENABLE should be updated where the status changes. */ static void __intel_pmu_disable_all(void) { @@ -1954,13 +1962,12 @@ static void __intel_pmu_disable_all(void) if (test_bit(INTEL_PMC_IDX_FIXED_BTS, cpuc->active_mask)) intel_pmu_disable_bts(); - - intel_pmu_pebs_disable_all(); } static void intel_pmu_disable_all(void) { __intel_pmu_disable_all(); + intel_pmu_pebs_disable_all(); intel_pmu_lbr_disable_all(); } @@ -1968,7 +1975,6 @@ static void __intel_pmu_enable_all(int added, bool pmi) { struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); - intel_pmu_pebs_enable_all(); intel_pmu_lbr_enable_all(pmi); wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, x86_pmu.intel_ctrl & ~cpuc->intel_ctrl_guest_mask); @@ -1986,6 +1992,7 @@ static void __intel_pmu_enable_all(int added, bool pmi) static void intel_pmu_enable_all(int added) { + intel_pmu_pebs_enable_all(); __intel_pmu_enable_all(added, false); } @@ -2374,9 +2381,21 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status) * PEBS overflow sets bit 62 in the global status register */ if (__test_and_clear_bit(62, (unsigned long *)&status)) { + u64 pebs_enabled = cpuc->pebs_enabled; + handled++; x86_pmu.drain_pebs(regs); status &= x86_pmu.intel_ctrl | GLOBAL_STATUS_TRACE_TOPAPMI; + + /* + * PMI throttle may be triggered, which stops the PEBS event. + * Although cpuc->pebs_enabled is updated accordingly, the + * MSR_IA32_PEBS_ENABLE is not updated. Because the + * cpuc->enabled has been forced to 0 in PMI. + * Update the MSR if pebs_enabled is changed. + */ + if (pebs_enabled != cpuc->pebs_enabled) + wrmsrl(MSR_IA32_PEBS_ENABLE, cpuc->pebs_enabled); } /*