[PATCH 09/11] perf, tools, stat: Basic support for TopDown in perf stat

From: Andi Kleen
Date: Wed Apr 27 2016 - 16:02:33 EST

From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

Add basic plumbing for TopDown in perf stat

Add a new --topdown options to enable events.
When --topdown is specified set up events for all topdown
events supported by the kernel.
Add topdown-* as a special case to the event parser, as is
needed for all events containing -.

The actual code to compute the metrics is in follow-on patches.

v2: Use standard sysctl read function.
v3: Move x86 specific code to arch/
v4: Enable --metric-only implicitly for topdown.
v5: Add --single-thread option to not force per core mode
v6: Fix output order of topdown metrics
v7: Allow combining with -d
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---
tools/perf/Documentation/perf-stat.txt | 24 +++++++
tools/perf/arch/x86/util/Build | 1 +
tools/perf/arch/x86/util/group.c | 27 ++++++++
tools/perf/builtin-stat.c | 115 ++++++++++++++++++++++++++++++++-
tools/perf/util/group.h | 7 ++
tools/perf/util/parse-events.l | 1 +
6 files changed, 172 insertions(+), 3 deletions(-)
create mode 100644 tools/perf/arch/x86/util/group.c
create mode 100644 tools/perf/util/group.h

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 04f23b404bbc..0b05d1f1139d 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -204,6 +204,30 @@ Aggregate counts per physical processor for system-wide mode measurements.
--no-aggr::
Do not aggregate counts across all monitored CPUs.

+--topdown::
+Print top down level 1 metrics if supported by the CPU. This allows to
+determine bottle necks in the CPU pipeline for CPU bound workloads,
+by breaking it down into frontend bound, backend bound, bad speculation
+and retiring. Metrics are only printed when they cross a threshold.
+
+The top down metrics may be collected per core instead of per
+CPU thread. In this case per core mode is automatically enabled
+and -a may need to be set, requiring root rights or
+perf.perf_event_paranoid=-1.
+
+This enable --metric-only, unless overriden with --no-metric-only.
+
+To interpret the results it is usually needed to know on which
+CPUs the workload runs on. If needed the CPUs can be forced using
+taskset.
+
+--single-thread::
+Don't force global per core mode with --topdown. The workload should
+work single threaded, otherwise the results may be unpredictable.
+
+This is generally only possible when the CPU does not use Hyper Threading
+or the secondary CPU threads have been offlined through
+/sys/devices/system/cpu/cpu*/online

EXAMPLES
--------
diff --git a/tools/perf/arch/x86/util/Build b/tools/perf/arch/x86/util/Build
index 465970370f3e..4cd8a16b1b7b 100644
--- a/tools/perf/arch/x86/util/Build
+++ b/tools/perf/arch/x86/util/Build
@@ -3,6 +3,7 @@ libperf-y += tsc.o
libperf-y += pmu.o
libperf-y += kvm-stat.o
libperf-y += perf_regs.o
+libperf-y += group.o

libperf-$(CONFIG_DWARF) += dwarf-regs.o
libperf-$(CONFIG_BPF_PROLOGUE) += dwarf-regs.o
diff --git a/tools/perf/arch/x86/util/group.c b/tools/perf/arch/x86/util/group.c
new file mode 100644
index 000000000000..f3039b5ce8b1
--- /dev/null
+++ b/tools/perf/arch/x86/util/group.c
@@ -0,0 +1,27 @@
+#include <stdio.h>
+#include "api/fs/fs.h"
+#include "util/group.h"
+
+/*
+ * Check whether we can use a group for top down.
+ * Without a group may get bad results due to multiplexing.
+ */
+bool check_group(bool *warn)
+{
+ int n;
+
+ if (sysctl__read_int("kernel/nmi_watchdog", &n) < 0)
+ return false;
+ if (n > 0) {
+ *warn = true;
+ return false;
+ }
+ return true;
+}
+
+void group_warn(void)
+{
+ fprintf(stderr,
+ "nmi_watchdog enabled with topdown. May give wrong results.\n"
+ "Disable with echo 0 > /proc/sys/kernel/nmi_watchdog\n");
+}
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 46c268eb123b..6d8ce72cd8c1 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -59,10 +59,13 @@
#include "util/thread.h"
#include "util/thread_map.h"
#include "util/counts.h"
+#include "util/group.h"
#include "util/session.h"
#include "util/tool.h"
+#include "util/group.h"
#include "asm/bug.h"

+#include <api/fs/fs.h>
#include <stdlib.h>
#include <sys/prctl.h>
#include <locale.h>
@@ -98,6 +101,15 @@ static const char * transaction_limited_attrs = {
"}"
};

+static const char * topdown_attrs[] = {
+ "topdown-total-slots",
+ "topdown-slots-retired",
+ "topdown-recovery-bubbles",
+ "topdown-fetch-bubbles",
+ "topdown-slots-issued",
+ NULL,
+};
+
static struct perf_evlist *evsel_list;

static struct target target = {
@@ -112,6 +124,8 @@ static volatile pid_t child_pid = -1;
static bool null_run = false;
static int detailed_run = 0;
static bool transaction_run;
+static bool topdown_run = false;
+static bool single_thread = false;
static bool big_num = true;
static int big_num_opt = -1;
static const char *csv_sep = NULL;
@@ -124,6 +138,7 @@ static unsigned int initial_delay = 0;
static unsigned int unit_width = 4; /* strlen("unit") */
static bool forever = false;
static bool metric_only = false;
+static bool force_metric_only = false;
static struct timespec ref_time;
static struct cpu_map *aggr_map;
static aggr_get_id_t aggr_get_id;
@@ -1507,6 +1522,14 @@ static int stat__set_big_num(const struct option *opt __maybe_unused,
return 0;
}

+static int enable_metric_only(const struct option *opt __maybe_unused,
+ const char *s __maybe_unused, int unset)
+{
+ force_metric_only = true;
+ metric_only = !unset;
+ return 0;
+}
+
static const struct option stat_options[] = {
OPT_BOOLEAN('T', "transaction", &transaction_run,
"hardware transaction statistics"),
@@ -1565,8 +1588,12 @@ static const struct option stat_options[] = {
"aggregate counts per thread", AGGR_THREAD),
OPT_UINTEGER('D', "delay", &initial_delay,
"ms to wait before starting measurement after program start"),
- OPT_BOOLEAN(0, "metric-only", &metric_only,
- "Only print computed metrics. No raw values"),
+ OPT_CALLBACK_NOOPT(0, "metric-only", &metric_only, NULL,
+ "Only print computed metrics. No raw values", enable_metric_only),
+ OPT_BOOLEAN(0, "topdown", &topdown_run,
+ "measure topdown level 1 statistics"),
+ OPT_BOOLEAN(0, "single-thread", &single_thread,
+ "don't force per core mode"),
OPT_END()
};

@@ -1759,12 +1786,61 @@ static int perf_stat_init_aggr_mode_file(struct perf_stat *st)
return 0;
}

+static void filter_events(const char **attr, char **str, bool use_group)
+{
+ int off = 0;
+ int i;
+ int len = 0;
+ char *s;
+
+ for (i = 0; attr[i]; i++) {
+ if (pmu_have_event("cpu", attr[i])) {
+ len += strlen(attr[i]) + 1;
+ attr[i - off] = attr[i];
+ } else
+ off++;
+ }
+ attr[i - off] = NULL;
+
+ *str = malloc(len + 1 + 2);
+ if (!*str)
+ return;
+ s = *str;
+ if (i - off == 0) {
+ *s = 0;
+ return;
+ }
+ if (use_group)
+ *s++ = '{';
+ for (i = 0; attr[i]; i++) {
+ strcpy(s, attr[i]);
+ s += strlen(s);
+ *s++ = ',';
+ }
+ if (use_group) {
+ s[-1] = '}';
+ *s = 0;
+ } else
+ s[-1] = 0;
+}
+
+__weak bool check_group(bool *warn)
+{
+ *warn = false;
+ return false;
+}
+
+__weak void group_warn(void)
+{
+}
+
/*
* Add default attributes, if there were no attributes specified or
* if -d/--detailed, -d -d or -d -d -d is used:
*/
static int add_default_attributes(void)
{
+ int err;
struct perf_event_attr default_attrs0[] = {

{ .type = PERF_TYPE_SOFTWARE, .config = PERF_COUNT_SW_TASK_CLOCK },
@@ -1883,7 +1959,6 @@ static int add_default_attributes(void)
return 0;

if (transaction_run) {
- int err;
if (pmu_have_event("cpu", "cycles-ct") &&
pmu_have_event("cpu", "el-start"))
err = parse_events(evsel_list, transaction_attrs, NULL);
@@ -1896,6 +1971,31 @@ static int add_default_attributes(void)
return 0;
}

+ if (topdown_run) {
+ char *str = NULL;
+ bool warn = false;
+
+ if (!force_metric_only)
+ metric_only = true;
+ filter_events(topdown_attrs, &str, check_group(&warn));
+ if (topdown_attrs[0] && str) {
+ if (warn)
+ group_warn();
+ err = parse_events(evsel_list, str, NULL);
+ if (err) {
+ fprintf(stderr,
+ "Cannot set up top down events %s: %d\n",
+ str, err);
+ free(str);
+ return -1;
+ }
+ } else {
+ fprintf(stderr, "System does not support topdown\n");
+ return -1;
+ }
+ free(str);
+ }
+
if (!evsel_list->nr_entries) {
if (perf_evlist__add_default_attrs(evsel_list, default_attrs0) < 0)
return -1;
@@ -2304,6 +2404,15 @@ int cmd_stat(int argc, const char **argv, const char *prefix __maybe_unused)
evlist__for_each (evsel_list, counter) {
/* Enable per core mode if only a single event requires it. */
if (counter->aggr_per_core) {
+ if (counter->aggr_per_core == 1 &&
+ single_thread)
+ continue;
+ else if (counter->aggr_per_core == 2 &&
+ single_thread) {
+ pr_err("single thread mode cannot be used with Hyper Threading enabled\n");
+ goto out;
+ }
+
if (stat_config.aggr_mode != AGGR_GLOBAL &&
stat_config.aggr_mode != AGGR_CORE) {
pr_err("per core event configuration requires per core mode\n");
diff --git a/tools/perf/util/group.h b/tools/perf/util/group.h
new file mode 100644
index 000000000000..daad3ffdc68d
--- /dev/null
+++ b/tools/perf/util/group.h
@@ -0,0 +1,7 @@
+#ifndef GROUP_H
+#define GROUP_H 1
+
+bool check_group(bool *warn);
+void group_warn(void);
+
+#endif
diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
index 1477fbc78993..744ebe3fa30f 100644
--- a/tools/perf/util/parse-events.l
+++ b/tools/perf/util/parse-events.l
@@ -259,6 +259,7 @@ cycles-ct { return str(yyscanner, PE_KERNEL_PMU_EVENT); }
cycles-t { return str(yyscanner, PE_KERNEL_PMU_EVENT); }
mem-loads { return str(yyscanner, PE_KERNEL_PMU_EVENT); }
mem-stores { return str(yyscanner, PE_KERNEL_PMU_EVENT); }
+topdown-[a-z-]+ { return str(yyscanner, PE_KERNEL_PMU_EVENT); }

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2.5.5