[PATCH v1 07/51] perf expr: Make the online topology accessible globally

From: Ian Rogers
Date: Sun Feb 19 2023 - 04:30:36 EST

Knowing the topology of online CPUs is useful for more than just expr
literals. Move to a global function that caches the value. An
additional upside is that this may also avoid computing the CPU
topology in some situations.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
tools/perf/tests/expr.c | 7 ++-----
tools/perf/util/cputopo.c | 14 ++++++++++++++
tools/perf/util/cputopo.h | 5 +++++
tools/perf/util/expr.c | 16 ++++++----------
tools/perf/util/smt.c | 11 +++++------
tools/perf/util/smt.h | 12 ++++++------
6 files changed, 38 insertions(+), 27 deletions(-)

diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
index a9eb1ed6bd63..cbf0e0c74906 100644
--- a/tools/perf/tests/expr.c
+++ b/tools/perf/tests/expr.c
@@ -154,13 +154,10 @@ static int test__expr(struct test_suite *t __maybe_unused, int subtest __maybe_u

/* Only EVENT1 or EVENT2 need be measured depending on the value of smt_on. */
{
- struct cpu_topology *topology = cpu_topology__new();
- bool smton = smt_on(topology);
+ bool smton = smt_on();
bool corewide = core_wide(/*system_wide=*/false,
- /*user_requested_cpus=*/false,
- topology);
+ /*user_requested_cpus=*/false);

- cpu_topology__delete(topology);
expr__ctx_clear(ctx);
TEST_ASSERT_VAL("find ids",
expr__find_ids("EVENT1 if #smt_on else EVENT2",
diff --git a/tools/perf/util/cputopo.c b/tools/perf/util/cputopo.c
index e08797c3cdbc..ca1d833a0c26 100644
--- a/tools/perf/util/cputopo.c
+++ b/tools/perf/util/cputopo.c
@@ -238,6 +238,20 @@ static bool has_die_topology(void)
return true;
}

+const struct cpu_topology *online_topology(void)
+{
+ static const struct cpu_topology *topology;
+
+ if (!topology) {
+ topology = cpu_topology__new();
+ if (!topology) {
+ pr_err("Error creating CPU topology");
+ abort();
+ }
+ }
+ return topology;
+}
+
struct cpu_topology *cpu_topology__new(void)
{
struct cpu_topology *tp = NULL;
diff --git a/tools/perf/util/cputopo.h b/tools/perf/util/cputopo.h
index 969e5920a00e..8d42f6102954 100644
--- a/tools/perf/util/cputopo.h
+++ b/tools/perf/util/cputopo.h
@@ -56,6 +56,11 @@ struct hybrid_topology {
struct hybrid_topology_node nodes[];
};

+/*
+ * The topology for online CPUs, lazily created.
+ */
+const struct cpu_topology *online_topology(void);
+
struct cpu_topology *cpu_topology__new(void);
void cpu_topology__delete(struct cpu_topology *tp);
/* Determine from the core list whether SMT was enabled. */
diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
index c1da20b868db..d46a1878bc9e 100644
--- a/tools/perf/util/expr.c
+++ b/tools/perf/util/expr.c
@@ -402,7 +402,7 @@ double arch_get_tsc_freq(void)

double expr__get_literal(const char *literal, const struct expr_scanner_ctx *ctx)
{
- static struct cpu_topology *topology;
+ const struct cpu_topology *topology;
double result = NAN;

if (!strcmp("#num_cpus", literal)) {
@@ -421,31 +421,27 @@ double expr__get_literal(const char *literal, const struct expr_scanner_ctx *ctx
* these strings gives an indication of the number of packages, dies,
* etc.
*/
- if (!topology) {
- topology = cpu_topology__new();
- if (!topology) {
- pr_err("Error creating CPU topology");
- goto out;
- }
- }
if (!strcasecmp("#smt_on", literal)) {
- result = smt_on(topology) ? 1.0 : 0.0;
+ result = smt_on() ? 1.0 : 0.0;
goto out;
}
if (!strcmp("#core_wide", literal)) {
- result = core_wide(ctx->system_wide, ctx->user_requested_cpu_list, topology)
+ result = core_wide(ctx->system_wide, ctx->user_requested_cpu_list)
? 1.0 : 0.0;
goto out;
}
if (!strcmp("#num_packages", literal)) {
+ topology = online_topology();
result = topology->package_cpus_lists;
goto out;
}
if (!strcmp("#num_dies", literal)) {
+ topology = online_topology();
result = topology->die_cpus_lists;
goto out;
}
if (!strcmp("#num_cores", literal)) {
+ topology = online_topology();
result = topology->core_cpus_lists;
goto out;
}
diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c
index 994e9e418227..650e804d0adc 100644
--- a/tools/perf/util/smt.c
+++ b/tools/perf/util/smt.c
@@ -4,7 +4,7 @@
#include "cputopo.h"
#include "smt.h"

-bool smt_on(const struct cpu_topology *topology)
+bool smt_on(void)
{
static bool cached;
static bool cached_result;
@@ -16,22 +16,21 @@ bool smt_on(const struct cpu_topology *topology)
if (sysfs__read_int("devices/system/cpu/smt/active", &fs_value) >= 0)
cached_result = (fs_value == 1);
else
- cached_result = cpu_topology__smt_on(topology);
+ cached_result = cpu_topology__smt_on(online_topology());

cached = true;
return cached_result;
}

-bool core_wide(bool system_wide, const char *user_requested_cpu_list,
- const struct cpu_topology *topology)
+bool core_wide(bool system_wide, const char *user_requested_cpu_list)
{
/* If not everything running on a core is being recorded then we can't use core_wide. */
if (!system_wide)
return false;

/* Cheap case that SMT is disabled and therefore we're inherently core_wide. */
- if (!smt_on(topology))
+ if (!smt_on())
return true;

- return cpu_topology__core_wide(topology, user_requested_cpu_list);
+ return cpu_topology__core_wide(online_topology(), user_requested_cpu_list);
}
diff --git a/tools/perf/util/smt.h b/tools/perf/util/smt.h
index ae9095f2c38c..01441fd2c0a2 100644
--- a/tools/perf/util/smt.h
+++ b/tools/perf/util/smt.h
@@ -2,16 +2,16 @@
#ifndef __SMT_H
#define __SMT_H 1

-struct cpu_topology;
-
-/* Returns true if SMT (aka hyperthreading) is enabled. */
-bool smt_on(const struct cpu_topology *topology);
+/*
+ * Returns true if SMT (aka hyperthreading) is enabled. Determined via sysfs or
+ * the online topology.
+ */
+bool smt_on(void);

/*
* Returns true when system wide and all SMT threads for a core are in the
* user_requested_cpus map.
*/
-bool core_wide(bool system_wide, const char *user_requested_cpu_list,
- const struct cpu_topology *topology);
+bool core_wide(bool system_wide, const char *user_requested_cpu_list);

#endif /* __SMT_H */
--
2.39.2.637.g21b0678d19-goog