[PATCH 05/10] perf, tools, stat: Basic support for TopDown in perf stat

Andi Kleen
2015-12-16T00:56:39Z

From: Andi Kleen <ak@linux.intel.com>

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.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
tools/perf/Documentation/perf-stat.txt | 8 +++
tools/perf/builtin-stat.c | 100 ++++++++++++++++++++++++++++++++-
tools/perf/util/parse-events.l | 1 +
3 files changed, 108 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 58296e7..9be9ac8 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -163,6 +163,14 @@ filter out the startup phase of the program, which is often very different.

Print statistics of transactional execution if supported.

+--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. Specifying the option multiple times shows metrics even
+if the don't cross a threshold.
+
EXAMPLES
--------

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 1faa6fc..e10198c 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -60,6 +60,7 @@
#include "util/thread_map.h"
#include "util/counts.h"

+#include <api/fs/fs.h>
#include <stdlib.h>
#include <sys/prctl.h>
#include <locale.h>
@@ -95,6 +96,15 @@ static const char * transaction_limited_attrs = {
"}"
};

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

static struct target target = {
@@ -109,6 +119,7 @@ static volatile pid_t child_pid = -1;
static bool null_run = false;
static int detailed_run = 0;
static bool transaction_run;
+static int topdown_run = 0;
static bool big_num = true;
static int big_num_opt = -1;
static const char *csv_sep = NULL;
@@ -1283,6 +1294,8 @@ static const struct option stat_options[] = {
"ms to wait before starting measurement after program start"),
OPT_BOOLEAN(0, "metric-only", &metric_only,
"Only print computed metrics. No raw values"),
+ OPT_INCR(0, "topdown", &topdown_run,
+ "measure topdown level 1 statistics"),
OPT_END()
};

@@ -1380,12 +1393,68 @@ static void perf_stat__exit_aggr_mode(void)
cpus_aggr_map = NULL;
}

+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;
+}
+
+/*
+ * Check whether we can use a group for top down.
+ * Without a group may get bad results due to multiplexing.
+ */
+static 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;
+}
+
/*
* 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_attrs[] = {

{ .type = PERF_TYPE_SOFTWARE, .config = PERF_COUNT_SW_TASK_CLOCK },
@@ -1498,7 +1567,6 @@ 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);
@@ -1511,6 +1579,36 @@ static int add_default_attributes(void)
return 0;
}

+ if (topdown_run) {
+ char *str = NULL;
+ bool warn = false;
+
+ filter_events(topdown_attrs, &str, check_group(&warn));
+ if (topdown_attrs[0] && str) {
+ if (warn)
+ fprintf(stderr,
+ "nmi_watchdog enabled with topdown. May give wrong results.\n"
+ "Disable with echo 0 > /proc/sys/kernel/nmi_watchdog\n");
+ 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);
+ /*
+ * Right now combining with the other attributes breaks group
+ * semantics.
+ */
+ return 0;
+ }
+
if (!evsel_list->nr_entries) {
if (perf_evlist__add_default_attrs(evsel_list, default_attrs) < 0)
return -1;
diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
index 58c5831..3e65d61 100644
--- a/tools/perf/util/parse-events.l
+++ b/tools/perf/util/parse-events.l
@@ -248,6 +248,7 @@ 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); }

L1-dcache|l1-d|l1d|L1-data |
L1-icache|l1-i|l1i|L1-instruction |
--
2.4.3