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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 67D5EC3F2D2 for ; Thu, 5 Mar 2020 21:02:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 361FA20684 for ; Thu, 5 Mar 2020 21:02:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726181AbgCEVCR (ORCPT ); Thu, 5 Mar 2020 16:02:17 -0500 Received: from mga09.intel.com ([134.134.136.24]:9691 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726092AbgCEVCQ (ORCPT ); Thu, 5 Mar 2020 16:02:16 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Mar 2020 13:02:14 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,519,1574150400"; d="scan'208";a="234566101" Received: from linux.intel.com ([10.54.29.200]) by fmsmga008.fm.intel.com with ESMTP; 05 Mar 2020 13:02:13 -0800 Received: from [10.251.16.243] (kliang2-mobl.ccr.corp.intel.com [10.251.16.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by linux.intel.com (Postfix) with ESMTPS id 219345802A3; Thu, 5 Mar 2020 13:02:12 -0800 (PST) Subject: Re: [PATCH 02/12] perf tools: Support PERF_SAMPLE_BRANCH_HW_INDEX To: Arnaldo Carvalho de Melo Cc: jolsa@redhat.com, peterz@infradead.org, mingo@redhat.com, linux-kernel@vger.kernel.org, namhyung@kernel.org, adrian.hunter@intel.com, mathieu.poirier@linaro.org, ravi.bangoria@linux.ibm.com, alexey.budankov@linux.intel.com, vitaly.slobodskoy@intel.com, pavel.gerasimov@intel.com, mpe@ellerman.id.au, eranian@google.com, ak@linux.intel.com References: <20200228163011.19358-1-kan.liang@linux.intel.com> <20200228163011.19358-3-kan.liang@linux.intel.com> <20200305202509.GA17483@kernel.org> From: "Liang, Kan" Message-ID: <74b01cee-12dc-2a95-9817-4f89a3fbd441@linux.intel.com> Date: Thu, 5 Mar 2020 16:02:10 -0500 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200305202509.GA17483@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/5/2020 3:25 PM, Arnaldo Carvalho de Melo wrote: > Em Fri, Feb 28, 2020 at 08:30:01AM -0800, kan.liang@linux.intel.com escreveu: >> From: Kan Liang >> >> A new branch sample type PERF_SAMPLE_BRANCH_HW_INDEX has been introduced >> in latest kernel. >> >> Enable HW_INDEX by default in LBR call stack mode. >> If kernel doesn't support the sample type, switching it off. >> >> Add HW_INDEX in attr_fprintf as well. User can check whether the branch >> sample type is set via debug information or header. > > So while this works with a kernel where PERF_SAMPLE_BRANCH_HW_INDEX is > present and we get, from the committer notes I was putting together > while testing/applying this cset: > > First collect some samples with LBR callchains, system wide, for a few > seconds: > > # perf record --call-graph lbr -a sleep 5 > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.625 MB perf.data (224 samples) ] > # > > Now lets use 'perf evlist -v' to look at the branch_sample_type: > > # perf evlist -v > cycles: size: 120, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK, read_format: ID, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, task: 1, precise_ip: 3, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1, branch_sample_type: USER|CALL_STACK|NO_FLAGS|NO_CYCLES|HW_INDEX > # > > So the machine has the kernel feature, and it was correctly added to > perf_event_attr.branch_sample_type, for the default 'cycles' event. > > Cool, and look at that 'attr.precise_ip: 3' part, the kernel is OK with > having that together with attr.branch_sample_type with HW_INDEX set. > > The problem happens when I go test this in an older kernel, where the > kernel doesn't know about HW_INDEX, we get it disabled but then > precise_ip is set to zero in its detection , even if at the end we get > it to 3, as expected, which got me a bit confused, I'll investigate this > a bit more to try and avoid these extra probes for the max precise level > that fails in older kernels due to branch_sample_type having HW_INDEX > :-\ It looks like this is an expected behavior for the event with maximum precise config for current perf tool. The related commits are as below: commit ID: 4e8a5c155137 ("perf evsel: Fix max perf_event_attr.precise_ip detection") commit ID: cd136189370c ("perf evsel: Do not rely on errno values for precise_ip fallback") Before handling any standard fallback (not just HW_INDEX), perf tool will try all the precise_ip value first. Thanks, Kan > > > # perf record -vv --call-graph lbr -a sleep 5 > > ------------------------------------------------------------ > perf_event_attr: > size 120 > { sample_period, sample_freq } 4000 > sample_type IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK > read_format ID > disabled 1 > inherit 1 > mmap 1 > comm 1 > freq 1 > task 1 > precise_ip 3 > sample_id_all 1 > exclude_guest 1 > mmap2 1 > comm_exec 1 > ksymbol 1 > bpf_event 1 > branch_sample_type USER|CALL_STACK|NO_FLAGS|NO_CYCLES|HW_INDEX > ------------------------------------------------------------ > sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 > sys_perf_event_open failed, error -95 > decreasing precise_ip by one (2) > ------------------------------------------------------------ > perf_event_attr: > size 120 > { sample_period, sample_freq } 4000 > sample_type IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK > read_format ID > disabled 1 > inherit 1 > mmap 1 > comm 1 > freq 1 > task 1 > precise_ip 2 > sample_id_all 1 > exclude_guest 1 > mmap2 1 > comm_exec 1 > ksymbol 1 > bpf_event 1 > branch_sample_type USER|CALL_STACK|NO_FLAGS|NO_CYCLES|HW_INDEX > ------------------------------------------------------------ > sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 > sys_perf_event_open failed, error -95 > decreasing precise_ip by one (1) > ------------------------------------------------------------ > perf_event_attr: > size 120 > { sample_period, sample_freq } 4000 > sample_type IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK > read_format ID > disabled 1 > inherit 1 > mmap 1 > comm 1 > freq 1 > task 1 > precise_ip 1 > sample_id_all 1 > exclude_guest 1 > mmap2 1 > comm_exec 1 > ksymbol 1 > bpf_event 1 > branch_sample_type USER|CALL_STACK|NO_FLAGS|NO_CYCLES|HW_INDEX > ------------------------------------------------------------ > sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 > sys_perf_event_open failed, error -95 > decreasing precise_ip by one (0) > ------------------------------------------------------------ > perf_event_attr: > size 120 > { sample_period, sample_freq } 4000 > sample_type IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK > read_format ID > disabled 1 > inherit 1 > mmap 1 > comm 1 > freq 1 > task 1 > sample_id_all 1 > exclude_guest 1 > mmap2 1 > comm_exec 1 > ksymbol 1 > bpf_event 1 > branch_sample_type USER|CALL_STACK|NO_FLAGS|NO_CYCLES|HW_INDEX > ------------------------------------------------------------ > sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 > sys_perf_event_open failed, error -22 > switching off branch HW index support > ------------------------------------------------------------ > perf_event_attr: > size 120 > { sample_period, sample_freq } 4000 > sample_type IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK > read_format ID > disabled 1 > inherit 1 > mmap 1 > comm 1 > freq 1 > task 1 > precise_ip 3 > sample_id_all 1 > exclude_guest 1 > mmap2 1 > comm_exec 1 > ksymbol 1 > bpf_event 1 > branch_sample_type USER|CALL_STACK|NO_FLAGS|NO_CYCLES > ------------------------------------------------------------ > > > >> Signed-off-by: Kan Liang >> --- >> tools/perf/util/evsel.c | 15 ++++++++++++--- >> tools/perf/util/evsel.h | 1 + >> tools/perf/util/perf_event_attr_fprintf.c | 1 + >> 3 files changed, 14 insertions(+), 3 deletions(-) >> >> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c >> index 05883a45de5b..816d930d774e 100644 >> --- a/tools/perf/util/evsel.c >> +++ b/tools/perf/util/evsel.c >> @@ -712,7 +712,8 @@ static void __perf_evsel__config_callchain(struct evsel *evsel, >> attr->branch_sample_type = PERF_SAMPLE_BRANCH_USER | >> PERF_SAMPLE_BRANCH_CALL_STACK | >> PERF_SAMPLE_BRANCH_NO_CYCLES | >> - PERF_SAMPLE_BRANCH_NO_FLAGS; >> + PERF_SAMPLE_BRANCH_NO_FLAGS | >> + PERF_SAMPLE_BRANCH_HW_INDEX; >> } >> } else >> pr_warning("Cannot use LBR callstack with branch stack. " >> @@ -763,7 +764,8 @@ perf_evsel__reset_callgraph(struct evsel *evsel, >> if (param->record_mode == CALLCHAIN_LBR) { >> perf_evsel__reset_sample_bit(evsel, BRANCH_STACK); >> attr->branch_sample_type &= ~(PERF_SAMPLE_BRANCH_USER | >> - PERF_SAMPLE_BRANCH_CALL_STACK); >> + PERF_SAMPLE_BRANCH_CALL_STACK | >> + PERF_SAMPLE_BRANCH_HW_INDEX); >> } >> if (param->record_mode == CALLCHAIN_DWARF) { >> perf_evsel__reset_sample_bit(evsel, REGS_USER); >> @@ -1673,6 +1675,8 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus, >> evsel->core.attr.ksymbol = 0; >> if (perf_missing_features.bpf) >> evsel->core.attr.bpf_event = 0; >> + if (perf_missing_features.branch_hw_idx) >> + evsel->core.attr.branch_sample_type &= ~PERF_SAMPLE_BRANCH_HW_INDEX; >> retry_sample_id: >> if (perf_missing_features.sample_id_all) >> evsel->core.attr.sample_id_all = 0; >> @@ -1784,7 +1788,12 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus, >> * Must probe features in the order they were added to the >> * perf_event_attr interface. >> */ >> - if (!perf_missing_features.aux_output && evsel->core.attr.aux_output) { >> + if (!perf_missing_features.branch_hw_idx && >> + (evsel->core.attr.branch_sample_type & PERF_SAMPLE_BRANCH_HW_INDEX)) { >> + perf_missing_features.branch_hw_idx = true; >> + pr_debug2("switching off branch HW index support\n"); >> + goto fallback_missing_features; >> + } else if (!perf_missing_features.aux_output && evsel->core.attr.aux_output) { >> perf_missing_features.aux_output = true; >> pr_debug2_peo("Kernel has no attr.aux_output support, bailing out\n"); >> goto out_close; >> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h >> index 99a0cb60c556..33804740e2ca 100644 >> --- a/tools/perf/util/evsel.h >> +++ b/tools/perf/util/evsel.h >> @@ -119,6 +119,7 @@ struct perf_missing_features { >> bool ksymbol; >> bool bpf; >> bool aux_output; >> + bool branch_hw_idx; >> }; >> >> extern struct perf_missing_features perf_missing_features; >> diff --git a/tools/perf/util/perf_event_attr_fprintf.c b/tools/perf/util/perf_event_attr_fprintf.c >> index 651203126c71..355d3458d4e6 100644 >> --- a/tools/perf/util/perf_event_attr_fprintf.c >> +++ b/tools/perf/util/perf_event_attr_fprintf.c >> @@ -50,6 +50,7 @@ static void __p_branch_sample_type(char *buf, size_t size, u64 value) >> bit_name(ABORT_TX), bit_name(IN_TX), bit_name(NO_TX), >> bit_name(COND), bit_name(CALL_STACK), bit_name(IND_JUMP), >> bit_name(CALL), bit_name(NO_FLAGS), bit_name(NO_CYCLES), >> + bit_name(HW_INDEX), >> { .name = NULL, } >> }; >> #undef bit_name >> -- >> 2.17.1 >> >