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Message-ID: <20250818171358.332331-2-thomas.falcon@intel.com>
Date: Mon, 18 Aug 2025 12:13:54 -0500
From: Thomas Falcon <thomas.falcon@...el.com>
To: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Kan Liang <kan.liang@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org,
ak@...ux.intel.com,
Thomas Falcon <thomas.falcon@...el.com>
Subject: [PATCH v2 1/2] perf record: Add ratio-to-prev term
Provide ratio-to-prev term which allows the user to
set the event sample period of two events corresponding
to a desired ratio. If using on an Intel x86 platform with
Auto Counter Reload support, also set corresponding event's
config2 attribute with a bitmask which counters to reset and
which counters to sample if the desired ratio is met or exceeded.
On other platforms, only the sample period is affected by the
ratio-to-prev term.
Signed-off-by: Thomas Falcon <thomas.falcon@...el.com>
---
tools/perf/Documentation/intel-acr.txt | 53 ++++++++++++++++++
tools/perf/Documentation/perf-list.txt | 2 +
tools/perf/arch/x86/util/evsel.c | 53 ++++++++++++++++++
tools/perf/util/evsel.c | 76 ++++++++++++++++++++++++++
tools/perf/util/evsel.h | 1 +
tools/perf/util/evsel_config.h | 1 +
tools/perf/util/parse-events.c | 22 ++++++++
tools/perf/util/parse-events.h | 3 +-
tools/perf/util/parse-events.l | 1 +
tools/perf/util/pmu.c | 3 +-
10 files changed, 213 insertions(+), 2 deletions(-)
create mode 100644 tools/perf/Documentation/intel-acr.txt
diff --git a/tools/perf/Documentation/intel-acr.txt b/tools/perf/Documentation/intel-acr.txt
new file mode 100644
index 000000000000..72654fdd9a52
--- /dev/null
+++ b/tools/perf/Documentation/intel-acr.txt
@@ -0,0 +1,53 @@
+Intel Auto Counter Reload Support
+---------------------------------
+Support for Intel Auto Counter Reload in perf tools
+
+Auto counter reload provides a means for software to specify to hardware
+that certain counters, if supported, should be automatically reloaded
+upon overflow of chosen counters. By taking a sample only if the rate of
+one event exceeds some threshold relative to the rate of another event,
+this feature enables software to sample based on the relative rate of
+two or more events. To enable this, the user must provide a sample period
+term and a bitmask ("acr_mask") for each relevant event specifying the
+counters in an event group to reload if the event's specified sample
+period is exceeded.
+
+For example, if the user desires to measure a scenario when IPC > 2,
+the event group might look like the one below:
+
+ perf record -e {cpu_atom/instructions,period=200000,acr_mask=0x2/, \
+ cpu_atom/cycles,period=100000,acr_mask=0x3/} -- true
+
+In this case, if the "instructions" counter exceeds the sample period of
+200000, the second counter, "cycles", will be reset and a sample will be
+taken. If "cycles" is exceeded first, both counters in the group will be
+reset. In this way, samples will only be taken for cases where IPC > 2.
+
+The acr_mask term is a hexadecimal value representing a bitmask of the
+events in the group to be reset when the period is exceeded. In the
+example above, "instructions" is assigned an acr_mask of 0x2, meaning
+only the second event in the group is reloaded and a sample is taken
+for the first event. "cycles" is assigned an acr_mask of 0x3, meaning
+that both event counters will be reset if the sample period is exceeded
+first.
+
+ratio-to-prev Event Term
+------------------------
+To simplify this, an event term "ratio-to-prev" is provided which is used
+alongside the sample period term n or the -c/--count option. This would
+allow users to specify the desired relative rate between events as a
+ratio. Note: Both events compared must belong to the same PMU.
+
+The command above would then become
+
+ perf record -e {cpu_atom/instructions/, \
+ cpu_atom/cycles,period=100000,ratio-to-prev=0.5/} -- true
+
+ratio-to-prev is the ratio of the event using the term relative
+to the previous event in the group, which will always be 1,
+for a 1:0.5 or 2:1 ratio.
+
+To sample for IPC < 2 for example, the events need to be reordered:
+
+ perf record -e {cpu_atom/cycles/, \
+ cpu_atom/instructions,period=200000,ratio-to-prev=2.0/} -- true
diff --git a/tools/perf/Documentation/perf-list.txt b/tools/perf/Documentation/perf-list.txt
index 28215306a78a..10bc66d39202 100644
--- a/tools/perf/Documentation/perf-list.txt
+++ b/tools/perf/Documentation/perf-list.txt
@@ -392,6 +392,8 @@ Support raw format:
. '--raw-dump [hw|sw|cache|tracepoint|pmu|event_glob]', shows the raw-dump of
a certain kind of events.
+include::intel-acr.txt[]
+
SEE ALSO
--------
linkperf:perf-stat[1], linkperf:perf-top[1],
diff --git a/tools/perf/arch/x86/util/evsel.c b/tools/perf/arch/x86/util/evsel.c
index 9bc80fff3aa0..84858e4c397d 100644
--- a/tools/perf/arch/x86/util/evsel.c
+++ b/tools/perf/arch/x86/util/evsel.c
@@ -1,7 +1,9 @@
// SPDX-License-Identifier: GPL-2.0
#include <stdio.h>
#include <stdlib.h>
+#include "util/evlist.h"
#include "util/evsel.h"
+#include "util/evsel_config.h"
#include "util/env.h"
#include "util/pmu.h"
#include "util/pmus.h"
@@ -67,6 +69,57 @@ int arch_evsel__hw_name(struct evsel *evsel, char *bf, size_t size)
event_name);
}
+void arch_evsel__apply_ratio_to_prev(struct evsel *evsel,
+ struct perf_event_attr *attr)
+{
+ struct perf_event_attr *prev_attr = NULL;
+ struct evsel *evsel_prev = NULL;
+ const char *name = "acr_mask";
+ int evsel_idx = 0;
+ __u64 ev_mask, pr_ev_mask;
+
+ if (!perf_pmu__has_format(evsel->pmu, name)) {
+ pr_err("'%s' does not have acr_mask format support\n", evsel->pmu->name);
+ return;
+ }
+ if (perf_pmu__format_type(evsel->pmu, name) !=
+ PERF_PMU_FORMAT_VALUE_CONFIG2) {
+ pr_err("'%s' does not have config2 format support\n", evsel->pmu->name);
+ return;
+ }
+
+ evsel_prev = evsel__prev(evsel);
+ if (!evsel_prev) {
+ pr_err("Previous event does not exist.\n");
+ return;
+ }
+
+ prev_attr = &evsel_prev->core.attr;
+
+ if (prev_attr->config2) {
+ pr_err("'%s' has set config2 (acr_mask?) already, configuration not supported\n", evsel_prev->name);
+ return;
+ }
+
+ /*
+ * acr_mask (config2) is calculated using the event's index in
+ * the event group. The first event will use the index of the
+ * second event as its mask (e.g., 0x2), indicating that the
+ * second event counter will be reset and a sample taken for
+ * the first event if its counter overflows. The second event
+ * will use the mask consisting of the first and second bits
+ * (e.g., 0x3), meaning both counters will be reset if the
+ * second event counter overflows.
+ */
+
+ evsel_idx = evsel__group_idx(evsel);
+ ev_mask = 1ull << evsel_idx;
+ pr_ev_mask = 1ull << (evsel_idx - 1);
+
+ prev_attr->config2 = ev_mask;
+ attr->config2 = ev_mask | pr_ev_mask;
+}
+
static void ibs_l3miss_warn(void)
{
pr_warning(
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index d264c143b592..f6f93920c0aa 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1091,6 +1091,71 @@ static void evsel__reset_callgraph(struct evsel *evsel, struct callchain_param *
}
}
+static void evsel__apply_ratio_to_prev(struct evsel *evsel,
+ struct perf_event_attr *attr,
+ struct record_opts *opts,
+ const char *buf)
+{
+ struct perf_event_attr *prev_attr = NULL;
+ struct evsel *evsel_prev = NULL;
+ u64 type = evsel->core.attr.sample_type;
+ u64 prev_type = 0;
+ double rtp;
+
+ rtp = strtod(buf, NULL);
+ if (rtp <= 0) {
+ pr_err("Invalid ratio-to-prev value %lf\n", rtp);
+ return;
+ }
+ if (evsel == evsel__leader(evsel)) {
+ pr_err("Invalid use of ratio-to-prev term without preceding element in group\n");
+ return;
+ }
+ if (!evsel->pmu->is_core) {
+ pr_err("Event using ratio-to-prev term must have a core PMU\n");
+ return;
+ }
+
+ evsel_prev = evsel__prev(evsel);
+ if (!evsel_prev) {
+ pr_err("Previous event does not exist.\n");
+ return;
+ }
+
+ if (evsel_prev->pmu->type != evsel->pmu->type) {
+ pr_err("Compared events (\"%s\", \"%s\") must have same PMU\n",
+ evsel->name, evsel_prev->name);
+ return;
+ }
+
+ prev_attr = &evsel_prev->core.attr;
+ prev_type = evsel_prev->core.attr.sample_type;
+
+ if (!(prev_type & PERF_SAMPLE_PERIOD)) {
+ attr->sample_period = prev_attr->sample_period * rtp;
+ attr->freq = 0;
+ evsel__reset_sample_bit(evsel, PERIOD);
+ } else if (!(type & PERF_SAMPLE_PERIOD)) {
+ prev_attr->sample_period = attr->sample_period / rtp;
+ prev_attr->freq = 0;
+ evsel__reset_sample_bit(evsel_prev, PERIOD);
+ } else {
+ if (opts->user_interval != ULLONG_MAX) {
+ prev_attr->sample_period = opts->user_interval;
+ attr->sample_period = prev_attr->sample_period * rtp;
+ prev_attr->freq = 0;
+ attr->freq = 0;
+ evsel__reset_sample_bit(evsel_prev, PERIOD);
+ evsel__reset_sample_bit(evsel, PERIOD);
+ } else {
+ pr_err("Event period term or count (-c) must be set when using ratio-to-prev term.\n");
+ return;
+ }
+ }
+
+ arch_evsel__apply_ratio_to_prev(evsel, attr);
+}
+
static void evsel__apply_config_terms(struct evsel *evsel,
struct record_opts *opts, bool track)
{
@@ -1104,6 +1169,7 @@ static void evsel__apply_config_terms(struct evsel *evsel,
u32 dump_size = 0;
int max_stack = 0;
const char *callgraph_buf = NULL;
+ const char *rtp_buf = NULL;
list_for_each_entry(term, config_terms, list) {
switch (term->type) {
@@ -1174,6 +1240,9 @@ static void evsel__apply_config_terms(struct evsel *evsel,
break;
case EVSEL__CONFIG_TERM_CFG_CHG:
break;
+ case EVSEL__CONFIG_TERM_RATIO_TO_PREV:
+ rtp_buf = term->val.str;
+ break;
default:
break;
}
@@ -1225,6 +1294,8 @@ static void evsel__apply_config_terms(struct evsel *evsel,
evsel__config_callchain(evsel, opts, ¶m);
}
}
+ if (rtp_buf)
+ evsel__apply_ratio_to_prev(evsel, attr, opts, rtp_buf);
}
struct evsel_config_term *__evsel__get_config_term(struct evsel *evsel, enum evsel_term_type type)
@@ -1249,6 +1320,11 @@ void __weak arch__post_evsel_config(struct evsel *evsel __maybe_unused,
{
}
+void __weak arch_evsel__apply_ratio_to_prev(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)
{
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 5797a02e5d6a..5002c795e818 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -342,6 +342,7 @@ void evsel__set_sample_id(struct evsel *evsel, bool use_sample_identifier);
void arch_evsel__set_sample_weight(struct evsel *evsel);
void arch__post_evsel_config(struct evsel *evsel, struct perf_event_attr *attr);
int arch_evsel__open_strerror(struct evsel *evsel, char *msg, size_t size);
+void arch_evsel__apply_ratio_to_prev(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);
diff --git a/tools/perf/util/evsel_config.h b/tools/perf/util/evsel_config.h
index 94a1e9cf73d6..bcd3a978f0c4 100644
--- a/tools/perf/util/evsel_config.h
+++ b/tools/perf/util/evsel_config.h
@@ -28,6 +28,7 @@ enum evsel_term_type {
EVSEL__CONFIG_TERM_AUX_ACTION,
EVSEL__CONFIG_TERM_AUX_SAMPLE_SIZE,
EVSEL__CONFIG_TERM_CFG_CHG,
+ EVSEL__CONFIG_TERM_RATIO_TO_PREV,
};
struct evsel_config_term {
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 8282ddf68b98..850de3a51f47 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -834,6 +834,7 @@ const char *parse_events__term_type_str(enum parse_events__term_type term_type)
[PARSE_EVENTS__TERM_TYPE_LEGACY_CACHE] = "legacy-cache",
[PARSE_EVENTS__TERM_TYPE_HARDWARE] = "hardware",
[PARSE_EVENTS__TERM_TYPE_CPU] = "cpu",
+ [PARSE_EVENTS__TERM_TYPE_RATIO_TO_PREV] = "ratio-to-prev",
};
if ((unsigned int)term_type >= __PARSE_EVENTS__TERM_TYPE_NR)
return "unknown term";
@@ -884,6 +885,7 @@ config_term_avail(enum parse_events__term_type term_type, struct parse_events_er
case PARSE_EVENTS__TERM_TYPE_RAW:
case PARSE_EVENTS__TERM_TYPE_LEGACY_CACHE:
case PARSE_EVENTS__TERM_TYPE_HARDWARE:
+ case PARSE_EVENTS__TERM_TYPE_RATIO_TO_PREV:
default:
if (!err)
return false;
@@ -1037,6 +1039,21 @@ do { \
perf_cpu_map__put(map);
break;
}
+ case PARSE_EVENTS__TERM_TYPE_RATIO_TO_PREV:
+ CHECK_TYPE_VAL(STR);
+ if (strtod(term->val.str, NULL) <= 0) {
+ parse_events_error__handle(err, term->err_val,
+ strdup("zero or negative"),
+ NULL);
+ return -EINVAL;
+ }
+ if (errno == ERANGE) {
+ parse_events_error__handle(err, term->err_val,
+ strdup("too big"),
+ NULL);
+ return -EINVAL;
+ }
+ break;
case PARSE_EVENTS__TERM_TYPE_DRV_CFG:
case PARSE_EVENTS__TERM_TYPE_USER:
case PARSE_EVENTS__TERM_TYPE_LEGACY_CACHE:
@@ -1165,6 +1182,7 @@ static int config_term_tracepoint(struct perf_event_attr *attr,
case PARSE_EVENTS__TERM_TYPE_LEGACY_CACHE:
case PARSE_EVENTS__TERM_TYPE_HARDWARE:
case PARSE_EVENTS__TERM_TYPE_CPU:
+ case PARSE_EVENTS__TERM_TYPE_RATIO_TO_PREV:
default:
if (err) {
parse_events_error__handle(err, term->err_term,
@@ -1289,6 +1307,9 @@ do { \
ADD_CONFIG_TERM_VAL(AUX_SAMPLE_SIZE, aux_sample_size,
term->val.num, term->weak);
break;
+ case PARSE_EVENTS__TERM_TYPE_RATIO_TO_PREV:
+ ADD_CONFIG_TERM_STR(RATIO_TO_PREV, term->val.str, term->weak);
+ break;
case PARSE_EVENTS__TERM_TYPE_USER:
case PARSE_EVENTS__TERM_TYPE_CONFIG:
case PARSE_EVENTS__TERM_TYPE_CONFIG1:
@@ -1355,6 +1376,7 @@ static int get_config_chgs(struct perf_pmu *pmu, struct parse_events_terms *head
case PARSE_EVENTS__TERM_TYPE_LEGACY_CACHE:
case PARSE_EVENTS__TERM_TYPE_HARDWARE:
case PARSE_EVENTS__TERM_TYPE_CPU:
+ case PARSE_EVENTS__TERM_TYPE_RATIO_TO_PREV:
default:
break;
}
diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
index 62dc7202e3ba..b2dcc52e3814 100644
--- a/tools/perf/util/parse-events.h
+++ b/tools/perf/util/parse-events.h
@@ -83,7 +83,8 @@ enum parse_events__term_type {
PARSE_EVENTS__TERM_TYPE_LEGACY_CACHE,
PARSE_EVENTS__TERM_TYPE_HARDWARE,
PARSE_EVENTS__TERM_TYPE_CPU,
-#define __PARSE_EVENTS__TERM_TYPE_NR (PARSE_EVENTS__TERM_TYPE_CPU + 1)
+ PARSE_EVENTS__TERM_TYPE_RATIO_TO_PREV,
+#define __PARSE_EVENTS__TERM_TYPE_NR (PARSE_EVENTS__TERM_TYPE_RATIO_TO_PREV + 1)
};
struct parse_events_term {
diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
index 2034590eb789..25206de68007 100644
--- a/tools/perf/util/parse-events.l
+++ b/tools/perf/util/parse-events.l
@@ -336,6 +336,7 @@ aux-action { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_AUX_ACTION); }
aux-sample-size { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_AUX_SAMPLE_SIZE); }
metric-id { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_METRIC_ID); }
cpu { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_CPU); }
+ratio-to-prev { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_RATIO_TO_PREV); }
cpu-cycles|cycles { return hw_term(yyscanner, PERF_COUNT_HW_CPU_CYCLES); }
stalled-cycles-frontend|idle-cycles-frontend { return hw_term(yyscanner, PERF_COUNT_HW_STALLED_CYCLES_FRONTEND); }
stalled-cycles-backend|idle-cycles-backend { return hw_term(yyscanner, PERF_COUNT_HW_STALLED_CYCLES_BACKEND); }
diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 5a291f1380ed..3d1f975e8db9 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -1541,7 +1541,7 @@ static int pmu_config_term(const struct perf_pmu *pmu,
break;
case PARSE_EVENTS__TERM_TYPE_USER: /* Not hardcoded. */
return -EINVAL;
- case PARSE_EVENTS__TERM_TYPE_NAME ... PARSE_EVENTS__TERM_TYPE_CPU:
+ case PARSE_EVENTS__TERM_TYPE_NAME ... PARSE_EVENTS__TERM_TYPE_RATIO_TO_PREV:
/* Skip non-config terms. */
break;
default:
@@ -1930,6 +1930,7 @@ int perf_pmu__for_each_format(struct perf_pmu *pmu, void *state, pmu_format_call
"aux-action=(pause|resume|start-paused)",
"aux-sample-size=number",
"cpu=number",
+ "ratio-to-prev=string",
};
struct perf_pmu_format *format;
int ret;
--
2.50.1
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