From 1e53e9d1787babb1544eaec7c7fdcb78a4a20a13 Mon Sep 17 00:00:00 2001 From: Dapeng Mi Date: Fri, 13 Sep 2024 08:47:08 +0000 Subject: [PATCH] perf x86/topdown: Correct leader selection with sample_read enabled 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. Reviewed-by: Kan Liang Signed-off-by: Dapeng Mi Cc: Yongwei Ma Link: https://lore.kernel.org/r/20240913084712.13861-3-dapeng1.mi@linux.intel.com Signed-off-by: Namhyung Kim --- tools/perf/arch/x86/util/topdown.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/tools/perf/arch/x86/util/topdown.c b/tools/perf/arch/x86/util/topdown.c index 49f25d67ed77..cb2c64928bc4 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 +88,24 @@ 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) { + if (evsel->core.leader != leader->core.leader) + return false; + if (evsel != leader && arch_is_topdown_metrics(evsel)) + return true; + } return false; } -- 2.50.1