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X-CSE-ConnectionGUID: ByIGr9HoT9muP+NL0dSVWA== X-CSE-MsgGUID: mfylf+kXSSqSQbkYDanrhA== X-IronPort-AV: E=McAfee;i="6700,10204,11162"; a="33079368" X-IronPort-AV: E=Sophos;i="6.09,285,1716274800"; d="scan'208";a="33079368" Received: from fmviesa001.fm.intel.com ([10.60.135.141]) by fmvoesa104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Aug 2024 00:15:14 -0700 X-CSE-ConnectionGUID: XtCBoT3QQdO13TBbAV0Ozw== X-CSE-MsgGUID: wdQa+sBiRMOFy78/AViuyw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.09,285,1716274800"; d="scan'208";a="89381705" Received: from dapengmi-mobl1.ccr.corp.intel.com (HELO [10.124.225.1]) ([10.124.225.1]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Aug 2024 00:15:11 -0700 Message-ID: Date: Tue, 13 Aug 2024 15:15:08 +0800 Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Patch v3 2/5] perf x86/topdown: Correct leader selection with sample_read enabled To: "Liang, Kan" , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Ian Rogers , Adrian Hunter , Alexander Shishkin Cc: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, Yongwei Ma , Dapeng Mi References: <20240712170339.185824-1-dapeng1.mi@linux.intel.com> <20240712170339.185824-3-dapeng1.mi@linux.intel.com> Content-Language: en-US From: "Mi, Dapeng" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/12/2024 11:18 PM, Liang, Kan wrote: > > On 2024-07-12 1:03 p.m., Dapeng Mi wrote: >> Addresses an issue where, in the absence of a topdown metrics event >> within a sampling group, the slots event was incorrectly bypassed as >> the sampling leader when sample_read was enabled. >> >> perf record -e '{slots,branches}:S' -c 10000 -vv sleep 1 >> >> In this case, the slots event should be sampled as leader but the >> branches event is sampled in fact like the verbose output shows. >> >> perf_event_attr: >> type 4 (cpu) >> size 168 >> config 0x400 (slots) >> sample_type IP|TID|TIME|READ|CPU|IDENTIFIER >> read_format ID|GROUP|LOST >> disabled 1 >> sample_id_all 1 >> exclude_guest 1 >> ------------------------------------------------------------ >> sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 = 5 >> ------------------------------------------------------------ >> perf_event_attr: >> type 0 (PERF_TYPE_HARDWARE) >> size 168 >> config 0x4 (PERF_COUNT_HW_BRANCH_INSTRUCTIONS) >> { sample_period, sample_freq } 10000 >> sample_type IP|TID|TIME|READ|CPU|IDENTIFIER >> read_format ID|GROUP|LOST >> sample_id_all 1 >> exclude_guest 1 >> >> The sample period of slots event instead of branches event is reset to >> 0. >> >> This fix ensures the slots event remains the leader under these >> conditions. >> >> Signed-off-by: Dapeng Mi >> --- >> tools/perf/arch/x86/util/topdown.c | 16 ++++++++++++++-- >> 1 file changed, 14 insertions(+), 2 deletions(-) >> >> diff --git a/tools/perf/arch/x86/util/topdown.c b/tools/perf/arch/x86/util/topdown.c >> index 49f25d67ed77..857e00cf579f 100644 >> --- a/tools/perf/arch/x86/util/topdown.c >> +++ b/tools/perf/arch/x86/util/topdown.c >> @@ -1,6 +1,7 @@ >> // SPDX-License-Identifier: GPL-2.0 >> #include "api/fs/fs.h" >> #include "util/evsel.h" >> +#include "util/evlist.h" >> #include "util/pmu.h" >> #include "util/pmus.h" >> #include "util/topdown.h" >> @@ -87,11 +88,22 @@ bool arch_is_topdown_metrics(const struct evsel *evsel) >> */ >> bool arch_topdown_sample_read(struct evsel *leader) >> { >> + struct evsel *evsel; >> + >> if (!evsel__sys_has_perf_metrics(leader)) >> return false; >> >> - if (arch_is_topdown_slots(leader)) >> - return true; >> + if (!arch_is_topdown_slots(leader)) >> + return false; >> + >> + /* >> + * If slots event as leader event but no topdown metric events >> + * in group, slots event should still sample as leader. >> + */ >> + evlist__for_each_entry(leader->evlist, evsel) { > evsel = leader->leader; > evlist__for_each_entry_continue(leader->evlist, evsel) > if (evsel->leader != leader->leader) > return false; > > Maybe we should limit the check in a group, rather than the entire > evlist. Something as above (not tested)? Good point. Would limit the check in the group. > > Thanks, > Kan >> + if (evsel != leader && arch_is_topdown_metrics(evsel)) >> + return true; >> + } >> >> return false; >> }