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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=no 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 E3A4BCA9EAF for ; Mon, 21 Oct 2019 20:04:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B46DB20873 for ; Mon, 21 Oct 2019 20:04:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730174AbfJUUET (ORCPT ); Mon, 21 Oct 2019 16:04:19 -0400 Received: from mga12.intel.com ([192.55.52.136]:57214 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726672AbfJUUET (ORCPT ); Mon, 21 Oct 2019 16:04:19 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Oct 2019 13:04:17 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,324,1566889200"; d="scan'208";a="201467354" Received: from labuser-ice-lake-client-platform.jf.intel.com ([10.54.55.125]) by orsmga006.jf.intel.com with ESMTP; 21 Oct 2019 13:04:17 -0700 From: kan.liang@linux.intel.com To: peterz@infradead.org, acme@kernel.org, mingo@kernel.org, linux-kernel@vger.kernel.org Cc: jolsa@kernel.org, namhyung@kernel.org, vitaly.slobodskoy@intel.com, pavel.gerasimov@intel.com, ak@linux.intel.com, eranian@google.com, Kan Liang Subject: [PATCH V2 00/13] Stitch LBR call stack Date: Mon, 21 Oct 2019 13:03:01 -0700 Message-Id: <20191021200314.1613-1-kan.liang@linux.intel.com> X-Mailer: git-send-email 2.17.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kan Liang Changes since V1 - Add a new branch sample type for LBR TOS. Drop the sample type in V1. - Add check in perf header to detect unknown input bits in event attr - Save and use the LBR cursor nodes from previous sample to avoid duplicate calculation of cursor nodes. - Add fast path for duplicate entries check. It benefits all call stack parsing, not just for stitch LBR call stack. It can be merged independetely. Start from Haswell, Linux perf can utilize the existing Last Branch Record (LBR) facility to record call stack. However, the depth of the reconstructed LBR call stack limits to the number of LBR registers. E.g. on skylake, the depth of reconstructed LBR call stack is <= 32 That's because HW will overwrite the oldest LBR registers when it's full. However, the overwritten LBRs may still be retrieved from previous sample. At that moment, HW hasn't overwritten the LBR registers yet. Perf tools can stitch those overwritten LBRs on current call stacks to get a more complete call stack. To determine if LBRs can be stitched, the physical index of LBR registers is required. A new branch sample type is introduced in patch 1 to 3 to dump the LBR Top-of-Stack (TOS) information for perf tools. Only when the new branch sample type is set, the TOS information is dumped into the PERF_SAMPLE_BRANCH_STACK output. Perf tool should check the attr.branch_sample_type, and apply the corresponding format for PERF_SAMPLE_BRANCH_STACK samples. The check is introduced in Patch 4. Besides, the maximum number of LBRs is required as well. Patch 5 & 6 retrieve the capabilities information from sysfs and save them in perf header. Patch 7 & 8 implements the LBR stitching approach. Users can use the options introduced in patch 9-12 to enable the LBR stitching approach for perf report, script, top and c2c. Patch 13 adds fast path for duplicate entries check. It benefits all call stack parsing, not just for stitch LBR call stack. It can be merged independetely. The stitching approach base on LBR call stack technology. The known limitations of LBR call stack technology still apply to the approach, e.g. Exception handing such as setjmp/longjmp will have calls/returns not match. This approach is not full proof. There can be cases where it creates incorrect call stacks from incorrect matches. There is no attempt to validate any matches in another way. So it is not enabled by default. However in many common cases with call stack overflows it can recreate better call stacks than the default lbr call stack output. So if there are problems with LBR overflows this is a possible workaround. Regression: Users may collect LBR call stack on a machine with new perf tool and new kernel (support LBR TOS). However, they may parse the perf.data with old perf tool (not support LBR TOS). The old tool doesn't check attr.branch_sample_type. Users probably get incorrect information without any warning. Performance impact: The processing time may increase with the LBR stitching approach enabled. The impact depends on the increased depth of call stacks. For a simple test case tchain_edit with 43 depth of call stacks. perf record --call-graph lbr -- ./tchain_edit perf report --stitch-lbr Without --stitch-lbr, perf report only display 32 depth of call stacks. With --stitch-lbr, perf report can display all 43 depth of call stacks. The depth of call stacks increase 34.3%. Correspondingly, the processing time of perf report increases 39%, Without --stitch-lbr: 11.0 sec With --stitch-lbr: 15.3 sec The source code of tchain_edit.c is something similar as below. noinline void f43(void) { int i; for (i = 0; i < 10000;) { if(i%2) i++; else i++; } } noinline void f42(void) { int i; for (i = 0; i < 100; i++) { f43(); f43(); f43(); } } noinline void f41(void) { int i; for (i = 0; i < 100; i++) { f42(); f42(); f42(); } } noinline void f40(void) { f41(); } ... ... noinline void f32(void) { f33(); } noinline void f31(void) { int i; for (i = 0; i < 10000; i++) { if(i%2) i++; else i++; } f32(); } noinline void f30(void) { f31(); } ... ... noinline void f1(void) { f2(); } int main() { f1(); } Kan Liang (13): perf/core: Add new branch sample type for LBR TOS perf/x86/intel: Output LBR TOS information perf tools: Support new branch sample type for LBR TOS perf header: Add check for event attr perf pmu: Add support for PMU capabilities perf header: Support CPU PMU capabilities perf machine: Refine the function for LBR call stack reconstruction perf tools: Stitch LBR call stack perf report: Add option to enable the LBR stitching approach perf script: Add option to enable the LBR stitching approach perf top: Add option to enable the LBR stitching approach perf c2c: Add option to enable the LBR stitching approach perf hist: Add fast path for duplicate entries check arch/x86/events/intel/core.c | 4 +- arch/x86/events/intel/ds.c | 5 +- arch/x86/events/intel/lbr.c | 9 + arch/x86/events/perf_event.h | 1 + include/linux/perf_event.h | 4 + include/uapi/linux/perf_event.h | 10 +- kernel/events/core.c | 10 + tools/include/uapi/linux/perf_event.h | 10 +- tools/perf/Documentation/perf-c2c.txt | 11 + tools/perf/Documentation/perf-report.txt | 11 + tools/perf/Documentation/perf-script.txt | 11 + tools/perf/Documentation/perf-top.txt | 9 + .../Documentation/perf.data-file-format.txt | 16 + tools/perf/builtin-c2c.c | 6 + tools/perf/builtin-record.c | 3 + tools/perf/builtin-report.c | 6 + tools/perf/builtin-script.c | 6 + tools/perf/builtin-stat.c | 1 + tools/perf/builtin-top.c | 11 + tools/perf/util/branch.h | 5 +- tools/perf/util/callchain.h | 12 +- tools/perf/util/env.h | 3 + tools/perf/util/event.h | 1 + tools/perf/util/evsel.c | 20 +- tools/perf/util/evsel.h | 6 + tools/perf/util/header.c | 148 +++++++ tools/perf/util/header.h | 1 + tools/perf/util/hist.c | 23 + tools/perf/util/machine.c | 408 +++++++++++++++--- tools/perf/util/parse-branch-options.c | 1 + tools/perf/util/perf_event_attr_fprintf.c | 1 + tools/perf/util/pmu.c | 87 ++++ tools/perf/util/pmu.h | 12 + tools/perf/util/sort.c | 2 +- tools/perf/util/sort.h | 2 + tools/perf/util/thread.c | 2 + tools/perf/util/thread.h | 34 ++ tools/perf/util/top.h | 1 + 38 files changed, 838 insertions(+), 75 deletions(-) -- 2.17.1