From: Ravi Bangoria <ravi.bangoria@amd.com>
To: <peterz@infradead.org>, <acme@kernel.org>
Cc: <ravi.bangoria@amd.com>, <rrichter@amd.com>, <mingo@redhat.com>,
<mark.rutland@arm.com>, <jolsa@kernel.org>, <namhyung@kernel.org>,
<tglx@linutronix.de>, <bp@alien8.de>, <irogers@google.com>,
<yao.jin@linux.intel.com>, <james.clark@arm.com>,
<leo.yan@linaro.org>, <kan.liang@linux.intel.com>,
<ak@linux.intel.com>, <eranian@google.com>,
<like.xu.linux@gmail.com>, <x86@kernel.org>,
<linux-perf-users@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <sandipan.das@amd.com>,
<ananth.narayan@amd.com>, <kim.phillips@amd.com>,
<santosh.shukla@amd.com>
Subject: [PATCH v2 5/8] perf record ibs: Warn about sampling period skew
Date: Mon, 9 May 2022 10:19:11 +0530 [thread overview]
Message-ID: <20220509044914.1473-6-ravi.bangoria@amd.com> (raw)
In-Reply-To: <20220509044914.1473-1-ravi.bangoria@amd.com>
Samples without an L3 miss are discarded and counter is reset with
random value (between 1-15 for fetch pmu and 1-127 for op pmu) when
IBS L3 miss filtering is enabled. This causes a sampling period skew
but there is no way to reconstruct aggregated sampling period. So
print a warning at perf record if user sets l3missonly=1.
Ex:
# perf record -c 10000 -C 0 -e ibs_op/l3missonly=1/
WARNING: Hw internally resets sampling period when L3 Miss Filtering is enabled
and tagged operation does not cause L3 Miss. This causes sampling period skew.
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
---
tools/perf/arch/x86/util/evsel.c | 34 ++++++++++++++++++++++++++++++++
tools/perf/util/evsel.c | 7 +++++++
tools/perf/util/evsel.h | 1 +
3 files changed, 42 insertions(+)
diff --git a/tools/perf/arch/x86/util/evsel.c b/tools/perf/arch/x86/util/evsel.c
index ac2899a25b7a..6399faa70a88 100644
--- a/tools/perf/arch/x86/util/evsel.c
+++ b/tools/perf/arch/x86/util/evsel.c
@@ -4,6 +4,8 @@
#include "util/evsel.h"
#include "util/env.h"
#include "linux/string.h"
+#include "util/pmu.h"
+#include "util/debug.h"
void arch_evsel__set_sample_weight(struct evsel *evsel)
{
@@ -29,3 +31,35 @@ void arch_evsel__fixup_new_cycles(struct perf_event_attr *attr)
free(env.cpuid);
}
+
+static void ibs_l3miss_warn(void)
+{
+ pr_warning(
+"WARNING: Hw internally resets sampling period when L3 Miss Filtering is enabled\n"
+"and tagged operation does not cause L3 Miss. This causes sampling period skew.\n");
+}
+
+void arch_evsel__warn_ambiguity(struct evsel *evsel, struct perf_event_attr *attr)
+{
+ struct perf_env *env = evsel__env(evsel);
+ struct perf_pmu *evsel_pmu = evsel__find_pmu(evsel);
+ struct perf_pmu *ibs_fetch_pmu = perf_pmu__find("ibs_fetch");
+ struct perf_pmu *ibs_op_pmu = perf_pmu__find("ibs_op");
+ static int warned_once;
+
+ if (warned_once || !perf_env__cpuid(env) || !env->cpuid ||
+ !strstarts(env->cpuid, "AuthenticAMD") || !evsel_pmu)
+ return;
+
+ if (ibs_fetch_pmu && ibs_fetch_pmu->type == evsel_pmu->type) {
+ if (attr->config & (1ULL << 59)) {
+ ibs_l3miss_warn();
+ warned_once = 1;
+ }
+ } else if (ibs_op_pmu && ibs_op_pmu->type == evsel_pmu->type) {
+ if (attr->config & (1ULL << 16)) {
+ ibs_l3miss_warn();
+ warned_once = 1;
+ }
+ }
+}
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 2a1729e7aee4..4f8b72d4a521 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1064,6 +1064,11 @@ void __weak arch_evsel__fixup_new_cycles(struct perf_event_attr *attr __maybe_un
{
}
+void __weak arch_evsel__warn_ambiguity(struct evsel *evsel __maybe_unused,
+ struct perf_event_attr *attr __maybe_unused)
+{
+}
+
static void evsel__set_default_freq_period(struct record_opts *opts,
struct perf_event_attr *attr)
{
@@ -1339,6 +1344,8 @@ void evsel__config(struct evsel *evsel, struct record_opts *opts,
*/
if (evsel__is_dummy_event(evsel))
evsel__reset_sample_bit(evsel, BRANCH_STACK);
+
+ arch_evsel__warn_ambiguity(evsel, attr);
}
int evsel__set_filter(struct evsel *evsel, const char *filter)
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 041b42d33bf5..195ae30ec45b 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -281,6 +281,7 @@ void evsel__set_sample_id(struct evsel *evsel, bool use_sample_identifier);
void arch_evsel__set_sample_weight(struct evsel *evsel);
void arch_evsel__fixup_new_cycles(struct perf_event_attr *attr);
+void arch_evsel__warn_ambiguity(struct evsel *evsel, struct perf_event_attr *attr);
int evsel__set_filter(struct evsel *evsel, const char *filter);
int evsel__append_tp_filter(struct evsel *evsel, const char *filter);
--
2.27.0
next prev parent reply other threads:[~2022-05-09 4:55 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-09 4:49 [PATCH v2 0/8] perf/amd: Zen4 IBS extensions support Ravi Bangoria
2022-05-09 4:49 ` [PATCH v2 1/8] perf/amd/ibs: Cascade pmu init functions' return value Ravi Bangoria
2022-05-11 19:47 ` [tip: perf/core] " tip-bot2 for Ravi Bangoria
2022-05-09 4:49 ` [PATCH v2 2/8] perf/amd/ibs: Use ->is_visible callback for dynamic attributes Ravi Bangoria
2022-05-11 19:47 ` [tip: perf/core] " tip-bot2 for Ravi Bangoria
2022-05-09 4:49 ` [PATCH v2 3/8] perf/amd/ibs: Add support for L3 miss filtering Ravi Bangoria
2022-05-09 12:05 ` Peter Zijlstra
2022-05-09 12:35 ` Ravi Bangoria
2022-05-09 13:07 ` Peter Zijlstra
2022-05-11 19:46 ` [tip: perf/core] " tip-bot2 for Ravi Bangoria
2022-05-09 4:49 ` [PATCH v2 4/8] perf/amd/ibs: Advertise zen4_ibs_extensions as pmu capability attribute Ravi Bangoria
2022-05-11 19:46 ` [tip: perf/core] " tip-bot2 for Ravi Bangoria
2022-05-09 4:49 ` Ravi Bangoria [this message]
2022-05-16 13:22 ` [PATCH v2 5/8] perf record ibs: Warn about sampling period skew Arnaldo Carvalho de Melo
2022-05-16 13:27 ` Ravi Bangoria
2022-05-09 4:49 ` [PATCH v2 6/8] perf header: Parse non-cpu pmu capabilities Ravi Bangoria
2022-05-16 4:15 ` Ravi Bangoria
2022-05-16 12:53 ` Arnaldo Carvalho de Melo
2022-05-16 13:28 ` Arnaldo Carvalho de Melo
2022-05-16 13:46 ` Ravi Bangoria
2022-05-09 4:49 ` [PATCH v2 7/8] perf script ibs: Support new IBS bits in raw trace dump Ravi Bangoria
2022-05-16 13:29 ` Arnaldo Carvalho de Melo
2022-05-16 13:47 ` Ravi Bangoria
2022-05-09 4:49 ` [PATCH v2 8/8] perf ibs: Fix comment Ravi Bangoria
2022-05-11 19:46 ` [tip: perf/core] perf/ibs: " tip-bot2 for Ravi Bangoria
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