* [PATCH v7 1/9] perf config: Move perf_config__set_variable() to util/config.c
2026-10-01 18:53 [PATCH v7 0/9] perf tools: Add progress diagnostics and a false-sharing workload Arnaldo Carvalho de Melo
@ 2026-10-01 18:53 ` Arnaldo Carvalho de Melo
2026-10-01 18:53 ` [PATCH v7 2/9] perf config: Make perf_etc_perfconfig() never return NULL Arnaldo Carvalho de Melo
` (7 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2026-10-01 18:53 UTC (permalink / raw)
To: Namhyung Kim
Cc: Ingo Molnar, Thomas Gleixner, James Clark, Jiri Olsa, Ian Rogers,
Adrian Hunter, Clark Williams, linux-kernel, linux-perf-users,
Arnaldo Carvalho de Melo
From: Arnaldo Carvalho de Melo <acme@redhat.com>
Move perf_config__set_variable() out of the 'perf config' builtin so
that opt-in features can persist their choice from outside it, e.g.
util/debuginfo.c writing core.debuginfod=false when the user disables
debuginfod for the rest of the session. The set_config() body becomes
perf_config_set__write(), with the system_config choice as an argument,
as the builtin's use_system_config/use_user_config statics are not
available outside it.
perf_config_set__write() checked fopen() but none of the fprintf()s or
fclose(), so a write failure after truncating the file was reported as
success. Harmless for the interactive 'perf config' this came from,
but this makes it an entry point a background feature can call with no
other feedback, so propagate those errors too.
Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-config.c | 70 +---------------------------------
tools/perf/util/config.c | 76 +++++++++++++++++++++++++++++++++++++
tools/perf/util/config.h | 2 +
3 files changed, 79 insertions(+), 69 deletions(-)
diff --git a/tools/perf/builtin-config.c b/tools/perf/builtin-config.c
index cefd042e4f853466..3b074aca8d344539 100644
--- a/tools/perf/builtin-config.c
+++ b/tools/perf/builtin-config.c
@@ -41,37 +41,7 @@ static struct option config_options[] = {
static int set_config(struct perf_config_set *set, const char *file_name)
{
- struct perf_config_section *section = NULL;
- struct perf_config_item *item = NULL;
- const char *first_line = "# this file is auto-generated.";
- FILE *fp;
-
- if (set == NULL)
- return -1;
-
- fp = fopen(file_name, "w");
- if (!fp)
- return -1;
-
- fprintf(fp, "%s\n", first_line);
-
- /* overwrite configvariables */
- perf_config_items__for_each_entry(&set->sections, section) {
- if (!use_system_config && section->from_system_config)
- continue;
- fprintf(fp, "[%s]\n", section->name);
-
- perf_config_items__for_each_entry(§ion->items, item) {
- if (!use_system_config && item->from_system_config)
- continue;
- if (item->value)
- fprintf(fp, "\t%s = %s\n",
- item->name, item->value);
- }
- }
- fclose(fp);
-
- return 0;
+ return perf_config_set__write(set, file_name, use_system_config);
}
static int show_spec_config(struct perf_config_set *set, const char *var)
@@ -158,44 +128,6 @@ static int parse_config_arg(char *arg, char **var, char **value)
return 0;
}
-int perf_config__set_variable(const char *var, const char *value)
-{
- char path[PATH_MAX];
- char *user_config = mkpath(path, sizeof(path), "%s/.perfconfig", getenv("HOME"));
- const char *config_filename;
- struct perf_config_set *set;
- int ret = -1;
-
- if (use_system_config)
- config_exclusive_filename = perf_etc_perfconfig();
- else if (use_user_config)
- config_exclusive_filename = user_config;
-
- if (!config_exclusive_filename)
- config_filename = user_config;
- else
- config_filename = config_exclusive_filename;
-
- set = perf_config_set__new();
- if (!set)
- goto out_err;
-
- if (perf_config_set__collect(set, config_filename, var, value) < 0) {
- pr_err("Failed to add '%s=%s'\n", var, value);
- goto out_err;
- }
-
- if (set_config(set, config_filename) < 0) {
- pr_err("Failed to set the configs on %s\n", config_filename);
- goto out_err;
- }
-
- ret = 0;
-out_err:
- perf_config_set__delete(set);
- return ret;
-}
-
int cmd_config(int argc, const char **argv)
{
int i, ret = -1;
diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index 8fe43b032e9af88a..85e50d0a25580da0 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -12,6 +12,7 @@
#include "config.h"
#include <errno.h>
+#include <limits.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
@@ -883,6 +884,81 @@ void perf_config__exit(void)
config_set = NULL;
}
+int perf_config_set__write(struct perf_config_set *set,
+ const char *file_name, bool system_config)
+{
+ struct perf_config_section *section = NULL;
+ struct perf_config_item *item = NULL;
+ int ret = 0;
+ FILE *fp;
+
+ fp = fopen(file_name, "w");
+ if (!fp)
+ return -1;
+
+ if (fprintf(fp, "# this file is auto-generated.\n") < 0)
+ ret = -1;
+
+ /* overwrite configvariables */
+ perf_config_sections__for_each_entry(&set->sections, section) {
+ if (!system_config && section->from_system_config)
+ continue;
+ if (fprintf(fp, "[%s]\n", section->name) < 0)
+ ret = -1;
+
+ perf_config_items__for_each_entry(§ion->items, item) {
+ if (!system_config && item->from_system_config)
+ continue;
+ if (item->value &&
+ fprintf(fp, "\t%s = %s\n", item->name, item->value) < 0)
+ ret = -1;
+ }
+ }
+ if (fclose(fp) != 0)
+ ret = -1;
+
+ return ret;
+}
+
+/*
+ * Set @var=@value in the config file perf is using: ~/.perfconfig or the
+ * file named by PERF_CONFIG. Same rewrite 'perf config' does, comments
+ * are not preserved.
+ */
+int perf_config__set_variable(const char *var, const char *value)
+{
+ char path[PATH_MAX];
+ char *user_config = mkpath(path, sizeof(path), "%s/.perfconfig", getenv("HOME"));
+ const char *config_filename;
+ bool system_config;
+ struct perf_config_set *set;
+ int ret = -1;
+
+ config_filename = config_exclusive_filename ?: user_config;
+
+ /* Rewriting the system wide file keeps its entries, or it is truncated. */
+ system_config = strcmp(config_filename, perf_etc_perfconfig()) == 0;
+
+ set = perf_config_set__new();
+ if (!set)
+ goto out_err;
+
+ if (perf_config_set__collect(set, config_filename, var, value) < 0) {
+ pr_err("Failed to add '%s=%s'\n", var, value);
+ goto out_err;
+ }
+
+ if (perf_config_set__write(set, config_filename, system_config) < 0) {
+ pr_err("Failed to set the configs on %s\n", config_filename);
+ goto out_err;
+ }
+
+ ret = 0;
+out_err:
+ perf_config_set__delete(set);
+ return ret;
+}
+
static void perf_config_item__delete(struct perf_config_item *item)
{
zfree(&item->name);
diff --git a/tools/perf/util/config.h b/tools/perf/util/config.h
index 987b47cf54c350ba..9098f8a045850c97 100644
--- a/tools/perf/util/config.h
+++ b/tools/perf/util/config.h
@@ -33,6 +33,8 @@ int perf_config_scan(const char *name, const char *fmt, ...) __scanf(2, 3);
const char *perf_config_get(const char *name);
int perf_config_set(struct perf_config_set *set,
config_fn_t fn, void *data);
+int perf_config_set__write(struct perf_config_set *set,
+ const char *file_name, bool system_config);
int perf_config_int(int *dest, const char *, const char *);
int perf_config_u8(u8 *dest, const char *name, const char *value);
int perf_config_u64(u64 *dest, const char *, const char *);
--
2.55.0
^ permalink raw reply [flat|nested] 10+ messages in thread* [PATCH v7 2/9] perf config: Make perf_etc_perfconfig() never return NULL
2026-10-01 18:53 [PATCH v7 0/9] perf tools: Add progress diagnostics and a false-sharing workload Arnaldo Carvalho de Melo
2026-10-01 18:53 ` [PATCH v7 1/9] perf config: Move perf_config__set_variable() to util/config.c Arnaldo Carvalho de Melo
@ 2026-10-01 18:53 ` Arnaldo Carvalho de Melo
2026-10-01 18:53 ` [PATCH v7 3/9] perf mutex: Add DEFINE_MUTEX() static initializer Arnaldo Carvalho de Melo
` (6 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2026-10-01 18:53 UTC (permalink / raw)
To: Namhyung Kim
Cc: Ingo Molnar, Thomas Gleixner, James Clark, Jiri Olsa, Ian Rogers,
Adrian Hunter, Clark Williams, linux-kernel, linux-perf-users,
Arnaldo Carvalho de Melo
From: Arnaldo Carvalho de Melo <acme@redhat.com>
perf_etc_perfconfig() returns what system_path() gives, and that
allocates, so on failure every caller dereferenced NULL, the
pre-existing ones in perf_config_set__init() and in the daemon
included. For the usual absolute ETC_PERFCONFIG system_path() just
returns a strdup of it, so use ETC_PERFCONFIG itself when that fails.
Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/config.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index 85e50d0a25580da0..6e0ff8a9140ccf96 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -571,8 +571,14 @@ static int perf_config_from_file(config_fn_t fn, const char *filename, void *dat
const char *perf_etc_perfconfig(void)
{
static const char *system_wide;
+
if (!system_wide)
- system_wide = system_path(ETC_PERFCONFIG);
+ /*
+ * ETC_PERFCONFIG is absolute, so its unresolved path is
+ * the same string, better than the callers crashing.
+ */
+ system_wide = system_path(ETC_PERFCONFIG) ?: ETC_PERFCONFIG;
+
return system_wide;
}
--
2.55.0
^ permalink raw reply [flat|nested] 10+ messages in thread* [PATCH v7 3/9] perf mutex: Add DEFINE_MUTEX() static initializer
2026-10-01 18:53 [PATCH v7 0/9] perf tools: Add progress diagnostics and a false-sharing workload Arnaldo Carvalho de Melo
2026-10-01 18:53 ` [PATCH v7 1/9] perf config: Move perf_config__set_variable() to util/config.c Arnaldo Carvalho de Melo
2026-10-01 18:53 ` [PATCH v7 2/9] perf config: Make perf_etc_perfconfig() never return NULL Arnaldo Carvalho de Melo
@ 2026-10-01 18:53 ` Arnaldo Carvalho de Melo
2026-10-01 18:53 ` [PATCH v7 4/9] perf mutex: Add DO_ONCE() for one-time initialization Arnaldo Carvalho de Melo
` (5 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2026-10-01 18:53 UTC (permalink / raw)
To: Namhyung Kim
Cc: Ingo Molnar, Thomas Gleixner, James Clark, Jiri Olsa, Ian Rogers,
Adrian Hunter, Clark Williams, linux-kernel, linux-perf-users,
Arnaldo Carvalho de Melo
From: Arnaldo Carvalho de Melo <acme@redhat.com>
For file scope mutexes, so that they don't need a constructor function
to initialize them at startup, mirroring PTHREAD_MUTEX_INITIALIZER
while keeping the clang -Wthread-safety annotations of struct mutex.
Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/mutex.h | 3 +++
1 file changed, 3 insertions(+)
diff --git a/tools/perf/util/mutex.h b/tools/perf/util/mutex.h
index 70232d8d094f8bfc..b85a80ad60386aed 100644
--- a/tools/perf/util/mutex.h
+++ b/tools/perf/util/mutex.h
@@ -92,6 +92,9 @@ struct LOCKABLE mutex {
pthread_mutex_t lock;
};
+/* Statically initialized mutex, for the file scope ones. */
+#define DEFINE_MUTEX(name) struct mutex name = { .lock = PTHREAD_MUTEX_INITIALIZER }
+
/* A wrapper around the condition variable implementation. */
struct cond {
pthread_cond_t cond;
--
2.55.0
^ permalink raw reply [flat|nested] 10+ messages in thread* [PATCH v7 4/9] perf mutex: Add DO_ONCE() for one-time initialization
2026-10-01 18:53 [PATCH v7 0/9] perf tools: Add progress diagnostics and a false-sharing workload Arnaldo Carvalho de Melo
` (2 preceding siblings ...)
2026-10-01 18:53 ` [PATCH v7 3/9] perf mutex: Add DEFINE_MUTEX() static initializer Arnaldo Carvalho de Melo
@ 2026-10-01 18:53 ` Arnaldo Carvalho de Melo
2026-10-01 18:53 ` [PATCH v7 5/9] perf config: Serialize config file access with a mutex Arnaldo Carvalho de Melo
` (4 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2026-10-01 18:53 UTC (permalink / raw)
To: Namhyung Kim
Cc: Ingo Molnar, Thomas Gleixner, James Clark, Jiri Olsa, Ian Rogers,
Adrian Hunter, Clark Williams, linux-kernel, linux-perf-users,
Arnaldo Carvalho de Melo
From: Arnaldo Carvalho de Melo <acme@redhat.com>
For lazy init that more than one thread can race into, without
pthread_once() so that it stays within perf's locking primitives and
clang's -Wthread-safety keeps an eye on the mutexes involved.
Mirrors the kernel's include/linux/once.h DO_ONCE(), dropping its
static key fast path, unnecessary at these cold init paths: a per call
site static bool plus a statically initialized mutex, double checked.
As there, code reachable from more than one call site must go through
a common helper.
Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/mutex.h | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/tools/perf/util/mutex.h b/tools/perf/util/mutex.h
index b85a80ad60386aed..87937970615ff675 100644
--- a/tools/perf/util/mutex.h
+++ b/tools/perf/util/mutex.h
@@ -95,6 +95,29 @@ struct LOCKABLE mutex {
/* Statically initialized mutex, for the file scope ones. */
#define DEFINE_MUTEX(name) struct mutex name = { .lock = PTHREAD_MUTEX_INITIALIZER }
+/*
+ * Runs fn() exactly once however many threads race to it, the rest wait
+ * for it to finish; per call site state, so multiple sites wanting the
+ * same once use a common helper, as in the kernel's DO_ONCE().
+ */
+#define DO_ONCE(fn, ...) \
+ ({ \
+ static bool ___done; \
+ static DEFINE_MUTEX(___once_lock); \
+ bool ___ret = false; \
+ \
+ if (!___done) { \
+ mutex_lock(&___once_lock); \
+ if (!___done) { \
+ fn(__VA_ARGS__); \
+ ___done = true; \
+ ___ret = true; \
+ } \
+ mutex_unlock(&___once_lock); \
+ } \
+ ___ret; \
+ })
+
/* A wrapper around the condition variable implementation. */
struct cond {
pthread_cond_t cond;
--
2.55.0
^ permalink raw reply [flat|nested] 10+ messages in thread* [PATCH v7 5/9] perf config: Serialize config file access with a mutex
2026-10-01 18:53 [PATCH v7 0/9] perf tools: Add progress diagnostics and a false-sharing workload Arnaldo Carvalho de Melo
` (3 preceding siblings ...)
2026-10-01 18:53 ` [PATCH v7 4/9] perf mutex: Add DO_ONCE() for one-time initialization Arnaldo Carvalho de Melo
@ 2026-10-01 18:53 ` Arnaldo Carvalho de Melo
2026-10-01 18:53 ` [PATCH v7 6/9] perf report: Add --progress option Arnaldo Carvalho de Melo
` (3 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2026-10-01 18:53 UTC (permalink / raw)
To: Namhyung Kim
Cc: Ingo Molnar, Thomas Gleixner, James Clark, Jiri Olsa, Ian Rogers,
Adrian Hunter, Clark Williams, linux-kernel, linux-perf-users,
Arnaldo Carvalho de Melo
From: Arnaldo Carvalho de Melo <acme@redhat.com>
Config file access shares the static parser state and, since
perf_config__set_variable() became an entry point for background
features, can run on more than one thread: a feature writing the
config while perf top's display thread reads it. Serialize parsing
and rewriting with config_mutex and the whole read-modify-write of
perf_config__set_variable() with config_update_mutex; config_set_mutex
comes before it, as building the set parses the config files.
perf has its own mutex type, util/mutex.h; the file scope mutexes
here use the DEFINE_MUTEX() static initializer added in the previous
patch. The two lazy inits that system_path() and home_perfconfig()
do would leak all but one of the strings racing on two threads, so
they move to DO_ONCE(), added in the previous patch as well.
bad_config() runs on the dispatching thread, outside config_mutex, so
it stops reading config_file_name, which the parsing thread owns.
Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/config.c | 106 +++++++++++++++++++++++++++------------
1 file changed, 73 insertions(+), 33 deletions(-)
diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index 6e0ff8a9140ccf96..287401f159e66e8c 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -31,6 +31,7 @@
#include "callchain.h"
#include "debug.h"
#include "header.h"
+#include "mutex.h"
#include "path.h"
#include "srcline.h"
#include "unwind.h"
@@ -371,10 +372,8 @@ static int perf_parse_long(const char *value, long *ret)
static void bad_config(const char *name)
{
- if (config_file_name)
- pr_warning("bad config value for '%s' in %s, ignoring...\n", name, config_file_name);
- else
- pr_warning("bad config value for '%s', ignoring...\n", name);
+ /* config_file_name is owned by the parsing thread, under config_mutex. */
+ pr_warning("bad config value for '%s', ignoring...\n", name);
}
int perf_config_u64(u64 *dest, const char *name, const char *value)
@@ -550,11 +549,18 @@ int perf_default_config(const char *var, const char *value,
return 0;
}
+/* Parsing and rewriting share the static parser state. */
+static DEFINE_MUTEX(config_mutex);
+
+/* Serializes whole perf_config__set_variable() updates. */
+static DEFINE_MUTEX(config_update_mutex);
+
static int perf_config_from_file(config_fn_t fn, const char *filename, void *data)
{
int ret;
FILE *f = fopen(filename, "r");
+ mutex_lock(&config_mutex);
ret = -1;
if (f) {
config_file = f;
@@ -565,21 +571,24 @@ static int perf_config_from_file(config_fn_t fn, const char *filename, void *dat
fclose(f);
config_file_name = NULL;
}
+ mutex_unlock(&config_mutex);
return ret;
}
-const char *perf_etc_perfconfig(void)
-{
- static const char *system_wide;
+/* system_path() allocates, so it is computed once. */
+static const char *etc_perfconfig;
- if (!system_wide)
- /*
- * ETC_PERFCONFIG is absolute, so its unresolved path is
- * the same string, better than the callers crashing.
- */
- system_wide = system_path(ETC_PERFCONFIG) ?: ETC_PERFCONFIG;
+static void perf_etc_perfconfig__init(void)
+{
+ etc_perfconfig = system_path(ETC_PERFCONFIG);
+ if (!etc_perfconfig)
+ etc_perfconfig = ETC_PERFCONFIG;
+}
- return system_wide;
+const char *perf_etc_perfconfig(void)
+{
+ DO_ONCE(perf_etc_perfconfig__init);
+ return etc_perfconfig;
}
static int perf_env_bool(const char *k, int def)
@@ -637,19 +646,18 @@ static char *home_perfconfig(void)
return NULL;
}
-const char *perf_home_perfconfig(void)
-{
- static const char *config;
- static bool failed;
-
- if (failed || config)
- return config;
+/* home_perfconfig() allocates and warns, so it is computed once. */
+static const char *home_config;
- config = home_perfconfig();
- if (!config)
- failed = true;
+static void perf_home_perfconfig__init(void)
+{
+ home_config = home_perfconfig();
+}
- return config;
+const char *perf_home_perfconfig(void)
+{
+ DO_ONCE(perf_home_perfconfig__init);
+ return home_config;
}
static struct perf_config_section *find_section(struct list_head *sections,
@@ -790,8 +798,15 @@ static int collect_config(const char *var, const char *value,
int perf_config_set__collect(struct perf_config_set *set, const char *file_name,
const char *var, const char *value)
{
+ int ret;
+
+ mutex_lock(&config_mutex);
config_file_name = file_name;
- return collect_config(var, value, set);
+ ret = collect_config(var, value, set);
+ /* Don't leave the static parser state pointing at the caller's buffer. */
+ config_file_name = NULL;
+ mutex_unlock(&config_mutex);
+ return ret;
}
static int perf_config_set__init(struct perf_config_set *set)
@@ -838,6 +853,10 @@ struct perf_config_set *perf_config_set__load_file(const char *file)
return set;
}
+/* Not config_mutex: building the set parses the config files, which takes it. */
+static DEFINE_MUTEX(config_set_mutex);
+
+/* Called with config_set_mutex held. */
static int perf_config__init(void)
{
if (config_set == NULL)
@@ -878,16 +897,26 @@ int perf_config_set(struct perf_config_set *set,
int perf_config(config_fn_t fn, void *data)
{
- if (config_set == NULL && perf_config__init())
+ struct perf_config_set *set;
+
+ /* Not held across the dispatch: a callback can call perf_config() again. */
+ mutex_lock(&config_set_mutex);
+ if (perf_config__init()) {
+ mutex_unlock(&config_set_mutex);
return -1;
+ }
+ set = config_set;
+ mutex_unlock(&config_set_mutex);
- return perf_config_set(config_set, fn, data);
+ return perf_config_set(set, fn, data);
}
void perf_config__exit(void)
{
+ mutex_lock(&config_set_mutex);
perf_config_set__delete(config_set);
config_set = NULL;
+ mutex_unlock(&config_set_mutex);
}
int perf_config_set__write(struct perf_config_set *set,
@@ -898,9 +927,12 @@ int perf_config_set__write(struct perf_config_set *set,
int ret = 0;
FILE *fp;
+ mutex_lock(&config_mutex);
fp = fopen(file_name, "w");
- if (!fp)
+ if (!fp) {
+ mutex_unlock(&config_mutex);
return -1;
+ }
if (fprintf(fp, "# this file is auto-generated.\n") < 0)
ret = -1;
@@ -922,6 +954,7 @@ int perf_config_set__write(struct perf_config_set *set,
}
if (fclose(fp) != 0)
ret = -1;
+ mutex_unlock(&config_mutex);
return ret;
}
@@ -933,14 +966,20 @@ int perf_config_set__write(struct perf_config_set *set,
*/
int perf_config__set_variable(const char *var, const char *value)
{
- char path[PATH_MAX];
- char *user_config = mkpath(path, sizeof(path), "%s/.perfconfig", getenv("HOME"));
const char *config_filename;
bool system_config;
- struct perf_config_set *set;
+ struct perf_config_set *set = NULL;
int ret = -1;
- config_filename = config_exclusive_filename ?: user_config;
+ mutex_lock(&config_update_mutex);
+
+ /* Static: the parser publishes it as config_file_name. */
+ {
+ static char path[PATH_MAX];
+ char *user_config = mkpath(path, sizeof(path), "%s/.perfconfig", getenv("HOME"));
+
+ config_filename = config_exclusive_filename ?: user_config;
+ }
/* Rewriting the system wide file keeps its entries, or it is truncated. */
system_config = strcmp(config_filename, perf_etc_perfconfig()) == 0;
@@ -962,6 +1001,7 @@ int perf_config__set_variable(const char *var, const char *value)
ret = 0;
out_err:
perf_config_set__delete(set);
+ mutex_unlock(&config_update_mutex);
return ret;
}
--
2.55.0
^ permalink raw reply [flat|nested] 10+ messages in thread* [PATCH v7 6/9] perf report: Add --progress option
2026-10-01 18:53 [PATCH v7 0/9] perf tools: Add progress diagnostics and a false-sharing workload Arnaldo Carvalho de Melo
` (4 preceding siblings ...)
2026-10-01 18:53 ` [PATCH v7 5/9] perf config: Serialize config file access with a mutex Arnaldo Carvalho de Melo
@ 2026-10-01 18:53 ` Arnaldo Carvalho de Melo
2026-10-01 18:53 ` [PATCH v7 7/9] perf report: Add --no-progress option Arnaldo Carvalho de Melo
` (2 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2026-10-01 18:53 UTC (permalink / raw)
To: Namhyung Kim
Cc: Ingo Molnar, Thomas Gleixner, James Clark, Jiri Olsa, Ian Rogers,
Adrian Hunter, Clark Williams, linux-kernel, linux-perf-users,
Arnaldo Carvalho de Melo
From: Arnaldo Carvalho de Melo <acme@redhat.com>
Processing a large session with stdio output gives no feedback about
which phase perf is in or how far along it is: ui_progress updates are
only shown by the TUI. Add --progress, installing a stdio backend
(ui/stdio/progress.c) that prints the phase title, percentage and
counts:
Processing events... [ 42.3%] 317M / 746M
Phases can be nested, so the backend tracks the ones started to
complete the right one on ui_progress__finish(); that requires
init()/finish() pairs, fixed in ordered-events.c and the pipe and
directory event processing.
Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/Documentation/perf-report.txt | 14 ++
tools/perf/builtin-report.c | 6 +
tools/perf/ui/Build | 1 +
tools/perf/ui/progress.h | 2 +
tools/perf/ui/stdio/progress.c | 162 +++++++++++++++++++++++
tools/perf/util/ordered-events.c | 16 ++-
tools/perf/util/session.c | 12 +-
7 files changed, 206 insertions(+), 7 deletions(-)
create mode 100644 tools/perf/ui/stdio/progress.c
diff --git a/tools/perf/Documentation/perf-report.txt b/tools/perf/Documentation/perf-report.txt
index 3718ebd297ce0673..a7429a30ec28f903 100644
--- a/tools/perf/Documentation/perf-report.txt
+++ b/tools/perf/Documentation/perf-report.txt
@@ -29,6 +29,20 @@ OPTIONS
--quiet::
Do not show any warnings or messages. (Suppress -v)
+--progress::
+ Show progress for each of the processing phases, printing the
+ percentage done and the current/total counts: the first phase
+ counts the bytes of the perf.data file processed so far, the
+ merge and sort phases count hist entries, e.g.:
+
+ Processing events... [ 42.3%] 4G / 10G
+ Merging related events... [ 7.1%] 1024 / 14387
+ Sorting events for output... [ 98.2%] 14132 / 14387
+
+ It is a no-op when using the TUI or GTK browsers, that already
+ present progress information, or when --quiet is used, that asks
+ for no messages at all.
+
-n::
--show-nr-samples::
Show the number of samples for each symbol
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 57225bc87731d074..81e13fb8194976c9 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -87,6 +87,7 @@ struct report {
bool use_gtk;
#endif
bool use_stdio;
+ bool progress;
bool show_full_info;
bool show_threads;
bool inverted_callchain;
@@ -1384,6 +1385,8 @@ int cmd_report(int argc, const char **argv)
"Use the stdio interface"),
OPT_BOOLEAN(0, "weights", &symbol_conf.annotate_weight,
"Show or hide weight columns in annotation. Default show if non-zero."),
+ OPT_BOOLEAN(0, "progress", &report.progress,
+ "Show progress while processing the perf.data file"),
OPT_BOOLEAN(0, "header", &report.header, "Show data header."),
OPT_BOOLEAN(0, "header-only", &report.header_only,
"Show only data header."),
@@ -1790,6 +1793,9 @@ int cmd_report(int argc, const char **argv)
else
use_browser = 0;
+ if (report.progress && !quiet && use_browser == 0)
+ stdio_progress__init();
+
if (report.data_type && use_browser == 1) {
symbol_conf.annotate_data_member = true;
symbol_conf.annotate_data_sample = true;
diff --git a/tools/perf/ui/Build b/tools/perf/ui/Build
index 6005f813c9e3990c..a7b1740d51c80f23 100644
--- a/tools/perf/ui/Build
+++ b/tools/perf/ui/Build
@@ -4,6 +4,7 @@ perf-ui-y += progress.o
perf-ui-y += util.o
perf-ui-y += hist.o
perf-ui-y += stdio/hist.o
+perf-ui-y += stdio/progress.o
CFLAGS_setup.o += -DLIBDIR="BUILD_STR($(LIBDIR))"
diff --git a/tools/perf/ui/progress.h b/tools/perf/ui/progress.h
index 4f52c37b2f099a82..03f1a8bb260ba076 100644
--- a/tools/perf/ui/progress.h
+++ b/tools/perf/ui/progress.h
@@ -23,6 +23,8 @@ void __ui_progress__init(struct ui_progress *p, u64 total,
void ui_progress__update(struct ui_progress *p, u64 adv);
+void stdio_progress__init(void);
+
struct ui_progress_ops {
void (*init)(struct ui_progress *p);
void (*update)(struct ui_progress *p);
diff --git a/tools/perf/ui/stdio/progress.c b/tools/perf/ui/stdio/progress.c
new file mode 100644
index 0000000000000000..118a6cf6555d59f5
--- /dev/null
+++ b/tools/perf/ui/stdio/progress.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Progress feedback for the stdio (non-TUI/GTK) case, enabled with
+ * 'perf report --progress'.
+ */
+#include <inttypes.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <linux/kernel.h>
+#include "../../util/debug.h"
+#include "../../util/units.h"
+#include "../progress.h"
+
+/*
+ * Phases can be nested, so keep track of the ones started so far to be
+ * able to complete the right one on ui_progress__finish(), which gets
+ * no arguments.
+ */
+#define STDIO_PROGRESS__MAX_DEPTH 8
+
+struct stdio_progress_phase {
+ struct ui_progress *p;
+ u64 last_printed;
+ size_t last_len;
+};
+
+static struct stdio_progress_phase stdio_progress__stack[STDIO_PROGRESS__MAX_DEPTH];
+static int stdio_progress__depth;
+static bool stdio_progress__is_tty;
+/* Phases that didn't fit on the stack are not shown. */
+static int stdio_progress__dropped;
+
+static void stdio_progress__print_phase(struct stdio_progress_phase *phase,
+ u64 curr)
+{
+ struct ui_progress *p = phase->p;
+ char buf_cur[20], buf_tot[20], buf[128];
+ double percent = p->total ? 100.0 * (double)curr / (double)p->total : 0.0;
+ size_t len;
+
+ /*
+ * Only the completion line shows 100.0%: a 99.99% progress would round
+ * up to it and look like a duplicate at finish time.
+ */
+ if (curr < p->total && percent > 99.9)
+ percent = 99.9;
+
+ if (p->size) {
+ unit_number__scnprintf(buf_cur, sizeof(buf_cur), curr);
+ unit_number__scnprintf(buf_tot, sizeof(buf_tot), p->total);
+ len = scnprintf(buf, sizeof(buf), "%s [%5.1f%%] %s / %s",
+ p->title, percent, buf_cur, buf_tot);
+ } else {
+ len = scnprintf(buf, sizeof(buf), "%s [%5.1f%%] %" PRIu64 " / %" PRIu64,
+ p->title, percent, curr, p->total);
+ }
+
+ if (!stdio_progress__is_tty) {
+ fprintf(stderr, "%s\n", buf);
+ goto out;
+ }
+
+ /* Pad to the length of the previous line to erase its leftovers. */
+ fprintf(stderr, "\r%s%*s", buf,
+ (int)(len < phase->last_len ? phase->last_len - len : 0), "");
+ phase->last_len = len;
+out:
+ phase->last_printed = curr;
+ fflush(stderr);
+}
+
+static void __stdio_progress__init(struct ui_progress *p)
+{
+ /* The default step is meant for the TUI bar, use 1% steps for stdio. */
+ p->next = p->step = p->total / 100 ?: 1;
+
+ if (stdio_progress__depth == STDIO_PROGRESS__MAX_DEPTH) {
+ /*
+ * Out of room: don't start this phase, its finish() is
+ * swallowed and its updates ignored below.
+ */
+ pr_warning("progress phases nested deeper than %d, not showing progress for %s\n",
+ STDIO_PROGRESS__MAX_DEPTH, p->title);
+ stdio_progress__dropped++;
+ return;
+ }
+
+ /* Start a nested phase in a line of its own. */
+ if (stdio_progress__depth && stdio_progress__is_tty)
+ fputc('\n', stderr);
+
+ stdio_progress__stack[stdio_progress__depth++] =
+ (struct stdio_progress_phase) {
+ .p = p,
+ .last_printed = 0,
+ .last_len = 0,
+ };
+
+ stdio_progress__print_phase(&stdio_progress__stack[stdio_progress__depth - 1],
+ p->curr);
+}
+
+static void stdio_progress__update(struct ui_progress *p)
+{
+ /*
+ * An update that doesn't match the innermost phase means something
+ * is out of sync: print nothing rather than another phase's
+ * numbers, or read past the stack.
+ */
+ if (!stdio_progress__depth ||
+ stdio_progress__stack[stdio_progress__depth - 1].p != p)
+ return;
+
+ stdio_progress__print_phase(&stdio_progress__stack[stdio_progress__depth - 1],
+ p->curr);
+}
+
+static void stdio_progress__finish(void)
+{
+ struct stdio_progress_phase *phase;
+
+ /*
+ * Being the innermost phase, its finish() comes first: swallow it, or
+ * it would complete the phase that encloses it.
+ */
+ if (stdio_progress__dropped) {
+ stdio_progress__dropped--;
+ return;
+ }
+
+ if (!stdio_progress__depth)
+ return;
+
+ phase = &stdio_progress__stack[--stdio_progress__depth];
+
+ /*
+ * The last line may have stopped short of the total, close this phase
+ * showing it as complete unless that was already printed.
+ */
+ if (phase->last_printed != phase->p->total)
+ stdio_progress__print_phase(phase, phase->p->total);
+
+ phase->last_printed = 0;
+ phase->last_len = 0;
+
+ if (stdio_progress__is_tty)
+ fputc('\n', stderr);
+
+ fflush(stderr);
+}
+
+static struct ui_progress_ops stdio_progress__ops = {
+ .init = __stdio_progress__init,
+ .update = stdio_progress__update,
+ .finish = stdio_progress__finish,
+};
+
+void stdio_progress__init(void)
+{
+ stdio_progress__is_tty = isatty(STDERR_FILENO) == 1;
+ ui_progress__ops = &stdio_progress__ops;
+}
diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c
index a5857f9f5af2d3de..54c85663e733be4d 100644
--- a/tools/perf/util/ordered-events.c
+++ b/tools/perf/util/ordered-events.c
@@ -237,14 +237,16 @@ static int do_flush(struct ordered_events *oe, bool show_progress)
ui_progress__init(&prog, oe->nr_events, "Processing time ordered events...");
list_for_each_entry_safe(iter, tmp, head, list) {
- if (session_done())
- return 0;
+ if (session_done()) {
+ ret = 0;
+ goto out_progress;
+ }
if (iter->timestamp > limit)
break;
ret = oe->deliver(oe, iter);
if (ret < 0)
- return ret;
+ goto out_progress;
ordered_events__delete(oe, iter);
oe->last_flush = iter->timestamp;
@@ -258,10 +260,16 @@ static int do_flush(struct ordered_events *oe, bool show_progress)
else if (last_ts <= limit)
oe->last = list_entry(head->prev, struct ordered_event, list);
+ ret = 0;
+out_progress:
+ /*
+ * Always pair ui_progress__init() with ui_progress__finish(), the
+ * stdio backend tracks the phases on a stack.
+ */
if (show_progress)
ui_progress__finish();
- return 0;
+ return ret;
}
static int __ordered_events__flush(struct ordered_events *oe, enum oe_flush how,
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 7fea9e72726c936c..c4b4c7fb3b864589 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -3253,8 +3253,12 @@ static int __perf_session__process_pipe_events(struct perf_session *session)
cur_size = sizeof(union perf_event);
buf = malloc(cur_size);
- if (!buf)
- return -errno;
+ if (!buf) {
+ err = -errno;
+ if (update_prog)
+ ui_progress__finish();
+ return err;
+ }
ordered_events__set_copy_on_queue(oe, true);
more:
event = buf;
@@ -3753,8 +3757,10 @@ static int __perf_session__process_dir_events(struct perf_session *session)
}
rd = calloc(nr_readers, sizeof(struct reader));
- if (!rd)
+ if (!rd) {
+ ui_progress__finish();
return -ENOMEM;
+ }
rd[0] = (struct reader) {
.fd = perf_data__fd(session->data),
--
2.55.0
^ permalink raw reply [flat|nested] 10+ messages in thread* [PATCH v7 7/9] perf report: Add --no-progress option
2026-10-01 18:53 [PATCH v7 0/9] perf tools: Add progress diagnostics and a false-sharing workload Arnaldo Carvalho de Melo
` (5 preceding siblings ...)
2026-10-01 18:53 ` [PATCH v7 6/9] perf report: Add --progress option Arnaldo Carvalho de Melo
@ 2026-10-01 18:53 ` Arnaldo Carvalho de Melo
2026-10-01 18:53 ` [PATCH v7 8/9] perf scripts: Add perf-stuck, to tell where a running perf is stuck Arnaldo Carvalho de Melo
2026-10-01 18:54 ` [PATCH v7 9/9] perf test: Add false_sharing workload exhibiting cross-CPU false sharing Arnaldo Carvalho de Melo
8 siblings, 0 replies; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2026-10-01 18:53 UTC (permalink / raw)
To: Namhyung Kim
Cc: Ingo Molnar, Thomas Gleixner, James Clark, Jiri Olsa, Ian Rogers,
Adrian Hunter, Clark Williams, linux-kernel, linux-perf-users,
Arnaldo Carvalho de Melo
From: Arnaldo Carvalho de Melo <acme@redhat.com>
Now that --progress is being added for the stdio case, wire up its
counterpart for the browsers: the TUI and GTK ones present progress of
their own and there is no way to turn it off. Install the no-op
ui_progress ops, the ones already used until a backend sets theirs,
after setup_browser() installed the ones of the browser in use. The
phases are still counted, nothing is shown for them, and no second
option is needed for it: parse-options provides --no-progress as the
negation of --progress, report.progress_set saying that it was asked
for, report.progress being false both when nothing was asked for and
when --no-progress was.
Suggested-by: Namhyung Kim <namhyung@kernel.org>
Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/Documentation/perf-report.txt | 5 +++++
tools/perf/builtin-report.c | 9 ++++++---
tools/perf/ui/progress.c | 6 ++++++
tools/perf/ui/progress.h | 2 ++
4 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/tools/perf/Documentation/perf-report.txt b/tools/perf/Documentation/perf-report.txt
index a7429a30ec28f903..e145124d6c9a1097 100644
--- a/tools/perf/Documentation/perf-report.txt
+++ b/tools/perf/Documentation/perf-report.txt
@@ -43,6 +43,11 @@ OPTIONS
present progress information, or when --quiet is used, that asks
for no messages at all.
+--no-progress::
+ Do not show progress while processing the perf.data file. It
+ also turns off the progress the TUI and GTK browsers present,
+ which is their own.
+
-n::
--show-nr-samples::
Show the number of samples for each symbol
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 81e13fb8194976c9..29085fdc91e58884 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -88,6 +88,7 @@ struct report {
#endif
bool use_stdio;
bool progress;
+ bool progress_set;
bool show_full_info;
bool show_threads;
bool inverted_callchain;
@@ -1385,8 +1386,8 @@ int cmd_report(int argc, const char **argv)
"Use the stdio interface"),
OPT_BOOLEAN(0, "weights", &symbol_conf.annotate_weight,
"Show or hide weight columns in annotation. Default show if non-zero."),
- OPT_BOOLEAN(0, "progress", &report.progress,
- "Show progress while processing the perf.data file"),
+ OPT_BOOLEAN_SET(0, "progress", &report.progress, &report.progress_set,
+ "Show progress while processing the perf.data file"),
OPT_BOOLEAN(0, "header", &report.header, "Show data header."),
OPT_BOOLEAN(0, "header-only", &report.header_only,
"Show only data header."),
@@ -1793,7 +1794,9 @@ int cmd_report(int argc, const char **argv)
else
use_browser = 0;
- if (report.progress && !quiet && use_browser == 0)
+ if (report.progress_set && !report.progress)
+ ui_progress__noop_init();
+ else if (report.progress && !quiet && use_browser == 0)
stdio_progress__init();
if (report.data_type && use_browser == 1) {
diff --git a/tools/perf/ui/progress.c b/tools/perf/ui/progress.c
index 99d60223c74b2957..362680989ace606a 100644
--- a/tools/perf/ui/progress.c
+++ b/tools/perf/ui/progress.c
@@ -13,6 +13,12 @@ static struct ui_progress_ops null_progress__ops =
struct ui_progress_ops *ui_progress__ops = &null_progress__ops;
+/* Everything counts but nothing is shown, the way it starts out. */
+void ui_progress__noop_init(void)
+{
+ ui_progress__ops = &null_progress__ops;
+}
+
void ui_progress__update(struct ui_progress *p, u64 adv)
{
u64 last = p->curr;
diff --git a/tools/perf/ui/progress.h b/tools/perf/ui/progress.h
index 03f1a8bb260ba076..e8c4f9f768aaf12b 100644
--- a/tools/perf/ui/progress.h
+++ b/tools/perf/ui/progress.h
@@ -25,6 +25,8 @@ void ui_progress__update(struct ui_progress *p, u64 adv);
void stdio_progress__init(void);
+void ui_progress__noop_init(void);
+
struct ui_progress_ops {
void (*init)(struct ui_progress *p);
void (*update)(struct ui_progress *p);
--
2.55.0
^ permalink raw reply [flat|nested] 10+ messages in thread* [PATCH v7 8/9] perf scripts: Add perf-stuck, to tell where a running perf is stuck
2026-10-01 18:53 [PATCH v7 0/9] perf tools: Add progress diagnostics and a false-sharing workload Arnaldo Carvalho de Melo
` (6 preceding siblings ...)
2026-10-01 18:53 ` [PATCH v7 7/9] perf report: Add --no-progress option Arnaldo Carvalho de Melo
@ 2026-10-01 18:53 ` Arnaldo Carvalho de Melo
2026-10-01 18:54 ` [PATCH v7 9/9] perf test: Add false_sharing workload exhibiting cross-CPU false sharing Arnaldo Carvalho de Melo
8 siblings, 0 replies; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2026-10-01 18:53 UTC (permalink / raw)
To: Namhyung Kim
Cc: Ingo Molnar, Thomas Gleixner, James Clark, Jiri Olsa, Ian Rogers,
Adrian Hunter, Clark Williams, linux-kernel, linux-perf-users,
Arnaldo Carvalho de Melo
From: Arnaldo Carvalho de Melo <acme@redhat.com>
A perf that takes forever is hard to tell apart from one stuck in a
loop, and there is no way to see where without attaching gdb.
perf-stuck.sh samples a running process' /proc entries and its progress
line at a fixed interval, and with -g runs gdb (perf-stuck.gdb, adding
the perf-die-chain command) when no progress is made across two
samples, printing the DIE chain a DWARF type chase is stuck in.
It is a prototype: the plan is to turn it into a first class 'perf
stuck' command. The process name is resolved with pgrep among the
caller's own processes only, as root an unscoped one would attach gdb
to the first process of any user with a matching name.
-i and -n are now validated instead of failing later inside the
sampling loop, -x now requires -g and gets the same readability check
as the default gdb command file, and gdb_done is cleared whenever
progress resumes, so -g can fire again on a later stall instead of at
most once per run.
Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/scripts/perf-stuck.gdb | 131 ++++++++++++++++++++
tools/perf/scripts/perf-stuck.sh | 193 ++++++++++++++++++++++++++++++
2 files changed, 324 insertions(+)
create mode 100644 tools/perf/scripts/perf-stuck.gdb
create mode 100755 tools/perf/scripts/perf-stuck.sh
diff --git a/tools/perf/scripts/perf-stuck.gdb b/tools/perf/scripts/perf-stuck.gdb
new file mode 100644
index 0000000000000000..b7f810198272ebf7
--- /dev/null
+++ b/tools/perf/scripts/perf-stuck.gdb
@@ -0,0 +1,131 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# gdb commands for a stuck perf, used by perf-stuck.sh -g and usable directly:
+#
+# gdb -p $(pgrep -x perf) -batch -x perf-stuck.gdb -ex bt
+#
+# PROTOTYPE: part of the perf-stuck.sh stopgap, wants to become a first
+# class 'perf stuck' command printing these DIE chains without gdb.
+#
+# The commands are for the DWARF type chasers in util/dwarf-aux.c:
+#
+# perf-die-chain <function> <die variable> [iterations]
+# perf-die-chain-all [iterations]
+# perf-dso
+#
+# For each iteration of the chasing loop they print the DIE address, the
+# CU, its file offset, tag and name: a cycle shows as the same (addr, cu)
+# pairs repeating, and a CU changing between iterations means the chase
+# hops between a debug file and its dwz common file.
+
+set pagination off
+set confirm off
+set debuginfod enabled off
+set print pretty on
+set height 0
+set width 0
+
+define perf-die-chain
+ if $argc < 2
+ printf "usage: perf-die-chain <function> <die variable> [iterations]\n"
+ else
+ frame function $arg0
+ if $argc == 3
+ set $perf_die_chain_n = $arg2
+ else
+ set $perf_die_chain_n = 10
+ end
+ set $perf_die_chain_head = $pc
+ set $perf_die_chain_i = 0
+ while $perf_die_chain_i < $perf_die_chain_n
+ # Pointer type DIEs have no DW_AT_name, so dwarf_diename() can
+ # return NULL: printf %s of it would error out and abort this
+ # batch script, handle it.
+ set $perf_die_chain_name = (char *) dwarf_diename($arg1)
+ printf "chain[%d] die=%p addr=%p cu=%p off=0x%lx tag=%d name=", \
+ $perf_die_chain_i, $arg1, $arg1->addr, $arg1->cu, \
+ ((Dwarf_Off) dwarf_dieoffset($arg1)), ((int) dwarf_tag($arg1))
+ if $perf_die_chain_name == 0
+ printf "(null)\n"
+ else
+ printf "%s\n", $perf_die_chain_name
+ end
+ until *$perf_die_chain_head
+ set $perf_die_chain_i = $perf_die_chain_i + 1
+ end
+ end
+end
+
+document perf-die-chain
+Print the DIE chain being walked by a DWARF type chasing loop.
+usage: perf-die-chain <function> <die variable> [iterations]
+ perf-die-chain die_get_pointer_type type_die
+ perf-die-chain __die_get_real_type vr_die
+ perf-die-chain die_get_real_type vr_die
+end
+
+define perf-die-chain-all
+ if $argc == 0
+ set $perf_die_chain_n = 10
+ else
+ set $perf_die_chain_n = $arg0
+ end
+ if $_any_caller_is("die_get_pointer_type", 20)
+ printf "stuck in die_get_pointer_type():\n"
+ perf-die-chain die_get_pointer_type type_die $perf_die_chain_n
+ else
+ if $_any_caller_is("__die_get_real_type", 20)
+ printf "stuck in __die_get_real_type():\n"
+ perf-die-chain __die_get_real_type vr_die $perf_die_chain_n
+ else
+ if $_any_caller_is("die_get_real_type", 20)
+ printf "stuck in die_get_real_type():\n"
+ perf-die-chain die_get_real_type vr_die $perf_die_chain_n
+ else
+ printf "not in a DWARF type chaser, try: bt\n"
+ end
+ end
+ end
+end
+
+document perf-die-chain-all
+Find which DWARF type chaser the process is in and print the DIE chain.
+usage: perf-die-chain-all [iterations]
+end
+
+define perf-dso
+ if $_any_caller_is("find_data_type", 20)
+ frame function find_data_type
+ # REFCNT_CHECKING, implied by an ASan/LSan build, wraps struct map and
+ # struct dso in a proxy keeping the real object in ->orig, the dso being
+ # map->orig->dso->orig there; struct symbol is not wrapped, so sym->name
+ # needs no ->orig. There is no way to ask gdb which layout it is looking
+ # at, so walk each candidate until one evaluates. Requiring gdb's Python
+ # here adds nothing: $_any_caller_is() is one of its functions already.
+ python
+import gdb
+
+dso = None
+for expr in ("dloc->ms->map->dso->name",
+ "dloc->ms->map->orig->dso->orig->name"):
+ try:
+ gdb.parse_and_eval(expr)
+ dso = expr
+ break
+ except gdb.error:
+ pass
+
+if dso is None:
+ print("dso=(no such member in struct map)")
+else:
+ gdb.execute('printf "dso=%s ip=0x%lx sym=%s\\n", ' + dso +
+ ', dloc->ip, dloc->ms->sym ? dloc->ms->sym->name : "(no symbol)"')
+ end
+ else
+ printf "not in find_data_type()\n"
+ end
+end
+
+document perf-dso
+Print the dso, ip and symbol of the data location being resolved.
+end
diff --git a/tools/perf/scripts/perf-stuck.sh b/tools/perf/scripts/perf-stuck.sh
new file mode 100755
index 0000000000000000..f9b545c107905a4e
--- /dev/null
+++ b/tools/perf/scripts/perf-stuck.sh
@@ -0,0 +1,193 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# perf-stuck - tell a spinning perf apart from a blocked or recursing one
+#
+# Arnaldo Carvalho de Melo <acme@redhat.com>
+#
+# PROTOTYPE: wants to become a first class 'perf stuck' command, sampling
+# a process from inside perf, with the knowledge of perf's phases and of
+# the DWARF type chasing loops built in, instead of poking /proc and
+# shelling out to gdb.
+#
+# Samples /proc/<pid> at a fixed interval and prints the CPU time used
+# since the previous sample, the [stack] mapping start and size, and the
+# last line of a progress log when one is given, e.g. the stderr of
+# 'perf report --progress': burning a full interval with a constant
+# stack is a loop, a [stack] start moving down is runaway recursion.
+#
+# With -g it runs gdb (perf-stuck.gdb) when no progress is made for two
+# consecutive samples, printing the DIE chain a DWARF type chase is
+# walking.
+#
+# usage: perf-stuck.sh [options] <pid|process-name>
+
+set -u
+
+usage() {
+ cat <<-EOF
+ usage: perf-stuck.sh [options] <pid|process-name>
+
+ -i <secs> sampling interval (default: 10)
+ -n <count> stop after this many samples (default: watch till it exits)
+ -l <file> progress log, its last line is printed with every sample
+ -g run gdb with perf-stuck.gdb when no progress is made for
+ two consecutive samples, writing the output to a temp file
+ -x <file> use this gdb command file instead of perf-stuck.gdb
+ -h this help
+ EOF
+ exit "${1:-0}"
+}
+
+interval=10
+count=0
+progress_log=
+use_gdb=
+gdb_cmds=
+
+while getopts "i:n:l:gx:h" opt; do
+ case "$opt" in
+ i) interval=$OPTARG ;;
+ n) count=$OPTARG ;;
+ l) progress_log=$OPTARG ;;
+ g) use_gdb=1 ;;
+ x) gdb_cmds=$OPTARG ;;
+ h) usage 0 ;;
+ *) usage 1 ;;
+ esac
+done
+shift $((OPTIND - 1))
+
+[[ "$interval" =~ ^[0-9]+$ ]] && [ "$interval" -gt 0 ] ||
+ { echo "-i wants a positive integer, got '$interval'"; usage 1; }
+[[ "$count" =~ ^[0-9]+$ ]] ||
+ { echo "-n wants a non-negative integer, got '$count'"; usage 1; }
+[ -n "$gdb_cmds" ] && [ -z "$use_gdb" ] && { echo "-x needs -g"; usage 1; }
+
+[ $# -eq 1 ] || usage 1
+
+if [[ "$1" =~ ^[0-9]+$ ]]; then
+ pid=$1
+else
+ # Resolve the name against the caller's own processes: as root,
+ # unscoped pgrep picks the first match of any user, e.g. one planted
+ # to get gdb attached to it, use an explicit pid to look at a perf of
+ # another user.
+ pid=$(pgrep -x -u "$(id -u)" -- "$1" | head -1)
+ [ -n "$pid" ] || { echo "no process named '$1' owned by $(id -un)"; exit 1; }
+fi
+
+[ -d /proc/"$pid" ] || { echo "no process $pid"; exit 1; }
+
+if [ -n "$use_gdb" ]; then
+ # Fail before watching, not two samples in when -g would fire.
+ command -v gdb > /dev/null || { echo "gdb not found, -g needs it"; exit 1; }
+ [ -z "$gdb_cmds" ] && gdb_cmds=$(dirname "$0")/perf-stuck.gdb
+ [ -r "$gdb_cmds" ] || { echo "cannot read $gdb_cmds"; exit 1; }
+fi
+
+hz=$(getconf CLK_TCK)
+psz=$(getconf PAGESIZE)
+prev_cpu=
+prev_stack=
+prev_progress=
+stuck=0
+gdb_done=
+nsample=0
+
+# The command line is whatever the process was started with, so drop the
+# control characters from it: a process started with escape sequences in
+# its arguments, e.g. one replaying a log line, would otherwise get them
+# replayed on the terminal of whoever runs this.
+cmdline=$(tr '\0' ' ' < /proc/"$pid"/cmdline | tr -d '[:cntrl:]')
+
+echo "watching $pid ($cmdline) every ${interval}s"
+
+while :; do
+ if [ ! -d /proc/"$pid" ]; then
+ echo "$(date +%T) process gone"
+ break
+ fi
+
+ # Field 2, the command name, is in parentheses and can contain
+ # spaces, so drop it together with the pid before splitting so the
+ # fields line up. %d keeps the CPU time out of scientific
+ # notation, that bash arithmetic can't parse past six digits.
+ if ! stat_line=$(awk '{ sub(/^[^ ]+ \(.*\) /, "");
+ printf "%s %d %d\n", $1, $12 + $13, $22 }' \
+ /proc/"$pid"/stat 2>/dev/null); then
+ echo "$(date +%T) process gone"
+ break
+ fi
+
+ # The process can be gone between the check above and this read, in
+ # which case there is nothing to report: 'set -u' would otherwise
+ # turn the unbound fields into an aborted script.
+ if [ -z "$stat_line" ]; then
+ echo "$(date +%T) process gone"
+ break
+ fi
+
+ stat=($stat_line)
+ state=${stat[0]}
+ cpu=${stat[1]}
+ # field 24 of /proc/<pid>/stat, the resident set size in pages
+ rss=$(( stat[2] * psz / 1024 ))
+
+ stack=$(awk '/\[stack\]/{print $1; exit}' /proc/"$pid"/maps 2>/dev/null)
+ if [ -n "$stack" ]; then
+ stack_start=0x${stack%-*}
+ stack_size=$(( 0x${stack#*-} - stack_start ))
+ stack_txt="$stack size=$((stack_size / 1024))kB"
+ else
+ stack_start=
+ stack_txt="-"
+ fi
+
+ progress=
+ [ -n "$progress_log" ] && [ -s "$progress_log" ] && progress=$(tail -1 -- "$progress_log")
+
+ if [ -n "$prev_cpu" ]; then
+ cpu_delta=$(( cpu - prev_cpu ))
+ # No progress log, or one with nothing written to it yet, leaves
+ # no progress to look at, so count the samples that show none:
+ # -g then looks at where the process is after two intervals.
+ # Otherwise count the repeats of the same last line.
+ if [ -z "$progress" ] || [ "$progress" = "$prev_progress" ]; then
+ stuck=$((stuck + 1))
+ else
+ stuck=0
+ gdb_done=
+ fi
+ stuck_txt="stuck=${stuck}"
+ [ "$stack_start" != "$prev_stack" ] && stuck_txt="$stuck_txt STACK"
+ else
+ cpu_delta=0
+ stuck_txt=""
+ fi
+
+ printf '%s state=%s cpu=+%d (%d.%02ds) rss=%dkB stack=%s %s %s\n' \
+ "$(date +%T)" "$state" "$cpu_delta" \
+ $(( cpu_delta / hz )) $(( (cpu_delta % hz) * 100 / hz )) \
+ "$rss" "$stack_txt" "$stuck_txt" "${progress:-(no progress log)}"
+
+ if [ -n "$use_gdb" ] && [ -z "$gdb_done" ] && [ "$stuck" -ge 2 ]; then
+ gdb_log=$(mktemp /tmp/perf-stuck-gdb.XXXXXX)
+ # The gdb script makes inferior calls, and a call into a perf
+ # wedged in a loop never returns, so bound the run; SIGINT
+ # releases the inferior instead of leaving perf stopped.
+ timeout --signal=INT 30 gdb -p "$pid" -batch -x "$gdb_cmds" -ex bt \
+ -ex 'perf-die-chain-all' -ex perf-dso -ex detach > "$gdb_log" 2>&1
+ gdb_done=1
+ echo "... gdb output of $pid in $gdb_log"
+ fi
+
+ prev_cpu=$cpu
+ prev_stack=$stack_start
+ prev_progress=$progress
+
+ nsample=$((nsample + 1))
+ [ "$count" -gt 0 ] && [ "$nsample" -ge "$count" ] && break
+
+ sleep "$interval"
+done
--
2.55.0
^ permalink raw reply [flat|nested] 10+ messages in thread* [PATCH v7 9/9] perf test: Add false_sharing workload exhibiting cross-CPU false sharing
2026-10-01 18:53 [PATCH v7 0/9] perf tools: Add progress diagnostics and a false-sharing workload Arnaldo Carvalho de Melo
` (7 preceding siblings ...)
2026-10-01 18:53 ` [PATCH v7 8/9] perf scripts: Add perf-stuck, to tell where a running perf is stuck Arnaldo Carvalho de Melo
@ 2026-10-01 18:54 ` Arnaldo Carvalho de Melo
8 siblings, 0 replies; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2026-10-01 18:54 UTC (permalink / raw)
To: Namhyung Kim
Cc: Ingo Molnar, Thomas Gleixner, James Clark, Jiri Olsa, Ian Rogers,
Adrian Hunter, Clark Williams, linux-kernel, linux-perf-users,
Arnaldo Carvalho de Melo
From: Arnaldo Carvalho de Melo <acme@redhat.com>
Add a 'perf test -w false_sharing' workload that hammers one shared
struct from several CPUs, shaped as a TCP connection: a read-mostly
identity (five-tuple) shares a cacheline with per-packet rx counters
(the false-sharing line), a second line has packet-path private tx and
congestion control counters, and a third the connection config.
The packet path runs in the main thread and up to four lookup threads
sum the five-tuple and pull the config, reading one volatile shared
instance directly so the accesses are PC-relative and resolvable by the
data type profiler.
Data type profiling of the workload with cacheline info:
$ perf mem record -- perf test -r5 -w false_sharing
[ perf record: Woken up 19 times to write data ]
[ perf record: Captured and wrote 5.612 MB perf.data (72454 samples) ]
$ perf report -s type,typecln -H --group --stdio
# Total Lost Samples: 0
#
# Samples: 72K of events 'cpu/mem-loads,ldlat=30/P, cpu/mem-stores/P'
# Event count (approx.): 1261814616
#
# Overhead Data Type / Data Type Cacheline
# ................... ...............................
#
88.99% 35.88% struct net_conn
56.43% 17.50% struct net_conn: cache-line 0
32.55% 0.00% struct net_conn: cache-line 2
0.01% 18.38% struct net_conn: cache-line 1
10.08% 63.03% (unknown)
10.08% 63.03% (unknown): cache-line 0
0.82% 0.13% int
0.82% 0.13% int: cache-line 0
0.01% 0.02% struct folio
0.01% 0.02% struct folio: cache-line 0
0.01% 0.03% Elf64_Addr
0.01% 0.03% Elf64_Addr: cache-line 0
0.01% 0.03% struct sched_entity
0.01% 0.03% struct sched_entity: cache-line 1
0.00% 0.00% struct sched_entity: cache-line 4
0.00% 0.00% struct sched_entity: cache-line 2
0.00% 0.00% struct sched_entity: cache-line 3
0.00% 0.00% struct sched_entity: cache-line 0
0.01% 0.00% struct task_group
0.01% 0.00% struct task_group: cache-line 4
0.00% 0.00% struct task_group: cache-line 5
0.00% 0.00% struct css_rstat_cpu
0.00% 0.00% struct css_rstat_cpu: cache-line 0
$ perf report -s type,typecln,typeoff -H --group --stdio
# Total Lost Samples: 0
#
# Samples: 72K of events 'cpu/mem-loads,ldlat=30/P, cpu/mem-stores/P'
# Event count (approx.): 1261814616
#
# Overhead Data Type / Data Type Cacheline / Data Type Offset
# ...................... ..................................................
#
88.99% 35.88% struct net_conn
56.43% 17.50% struct net_conn: cache-line 0
9.81% 0.00% struct net_conn +0xa (dport)
9.54% 0.00% struct net_conn +0x8 (sport)
9.53% 0.00% struct net_conn +0xc (state)
9.48% 0.00% struct net_conn +0xd (protocol)
9.27% 0.00% struct net_conn +0x4 (daddr)
8.79% 0.00% struct net_conn +0 (saddr)
0.00% 12.08% struct net_conn +0x10 (bytes_rx)
0.00% 1.71% struct net_conn +0x18 (packets_rx)
0.00% 2.80% struct net_conn +0x20 (rx_queue)
0.00% 0.91% struct net_conn +0x3c (last_ack)
32.55% 0.00% struct net_conn: cache-line 2
5.70% 0.00% struct net_conn +0x83 (rcv_wscale)
5.46% 0.00% struct net_conn +0x84 (keepalive_int)
5.43% 0.00% struct net_conn +0x82 (snd_wscale)
5.39% 0.00% struct net_conn +0x80 (mss)
5.34% 0.00% struct net_conn +0x88 (mark)
5.23% 0.00% struct net_conn +0x8c (priority)
0.01% 18.38% struct net_conn: cache-line 1
0.01% 0.05% struct net_conn +0x5c (retrans)
0.00% 4.83% struct net_conn +0x40 (bytes_tx)
0.00% 10.63% struct net_conn +0x48 (packets_tx)
0.00% 1.54% struct net_conn +0x58 (rtt_us)
0.00% 1.07% struct net_conn +0x50 (cwnd)
0.00% 0.25% struct net_conn +0x54 (ssthresh)
10.08% 63.03% (unknown)
10.08% 63.03% (unknown): cache-line 0
10.08% 63.03% (unknown)
0.82% 0.13% int
0.82% 0.13% int: cache-line 0
0.82% 0.13% int +0 (no field)
0.01% 0.02% struct folio
0.01% 0.02% struct folio: cache-line 0
0.01% 0.00% struct folio +0 (flags.f)
0.00% 0.01% struct folio +0x34 (_refcount.counter)
0.00% 0.00% struct folio +0x18 (mapping)
Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/tests/builtin-test.c | 1 +
tools/perf/tests/shell/data_type_profiling.sh | 9 +-
tools/perf/tests/tests.h | 1 +
tools/perf/tests/workloads/Build | 2 +
tools/perf/tests/workloads/false_sharing.c | 251 ++++++++++++++++++
5 files changed, 262 insertions(+), 2 deletions(-)
create mode 100644 tools/perf/tests/workloads/false_sharing.c
diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
index d2f594921e25bda9..98134b1c74cf80f4 100644
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c
@@ -175,6 +175,7 @@ static struct test_workload *workloads[] = {
&workload__context_switch_loop,
&workload__deterministic,
&workload__callchain,
+ &workload__false_sharing,
#ifdef HAVE_RUST_SUPPORT
&workload__code_with_type,
diff --git a/tools/perf/tests/shell/data_type_profiling.sh b/tools/perf/tests/shell/data_type_profiling.sh
index a916c410274aa888..57203e0e5f857540 100755
--- a/tools/perf/tests/shell/data_type_profiling.sh
+++ b/tools/perf/tests/shell/data_type_profiling.sh
@@ -8,8 +8,8 @@ set -e
# data type profiling manifestation
# Values in testtypes and testprogs should match
-testtypes=("# data-type: struct Buf" "# data-type: struct buf")
-testprogs=("perf test -w code_with_type" "perf test -w datasym")
+testtypes=("# data-type: struct Buf" "# data-type: struct buf" "# data-type: struct net_conn")
+testprogs=("perf test -w code_with_type" "perf test -w datasym" "perf test -w false_sharing")
err=0
perfdata=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
@@ -59,6 +59,9 @@ test_basic_annotate() {
"xC")
index=1 ;;
+
+ "xFS")
+ index=2 ;;
esac
# Under 'set -e' a bare failing command aborts the script through the EXIT
@@ -114,6 +117,8 @@ test_basic_annotate Basic Rust
test_basic_annotate Pipe Rust
test_basic_annotate Basic C
test_basic_annotate Pipe C
+test_basic_annotate Basic FS
+test_basic_annotate Pipe FS
cleanup
exit $err
diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
index 9c96f33483d14356..f379620069d34f3a 100644
--- a/tools/perf/tests/tests.h
+++ b/tools/perf/tests/tests.h
@@ -250,6 +250,7 @@ DECLARE_WORKLOAD(jitdump);
DECLARE_WORKLOAD(context_switch_loop);
DECLARE_WORKLOAD(deterministic);
DECLARE_WORKLOAD(callchain);
+DECLARE_WORKLOAD(false_sharing);
#ifdef HAVE_RUST_SUPPORT
DECLARE_WORKLOAD(code_with_type);
diff --git a/tools/perf/tests/workloads/Build b/tools/perf/tests/workloads/Build
index 048e371eb63e3164..18fceddccb56c013 100644
--- a/tools/perf/tests/workloads/Build
+++ b/tools/perf/tests/workloads/Build
@@ -14,6 +14,7 @@ perf-test-y += jitdump.o
perf-test-y += context_switch_loop.o
perf-test-y += deterministic.o
perf-test-y += callchain.o
+perf-test-y += false_sharing.o
ifeq ($(CONFIG_RUST_SUPPORT),y)
perf-test-y += code_with_type.o
@@ -29,3 +30,4 @@ CFLAGS_inlineloop.o = -g -O2
CFLAGS_deterministic.o = -g -O0 -fno-inline -U_FORTIFY_SOURCE
CFLAGS_named_threads.o = -g -O0 -fno-inline -U_FORTIFY_SOURCE
CFLAGS_callchain.o = -g -O0 -fno-inline -U_FORTIFY_SOURCE
+CFLAGS_false_sharing.o = -g -O0 -fno-inline -U_FORTIFY_SOURCE
diff --git a/tools/perf/tests/workloads/false_sharing.c b/tools/perf/tests/workloads/false_sharing.c
new file mode 100644
index 0000000000000000..e949bb36646a97a5
--- /dev/null
+++ b/tools/perf/tests/workloads/false_sharing.c
@@ -0,0 +1,251 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * False-sharing demo for data type profiling, shaped as a TCP
+ * connection: a read-mostly identity shares a cacheline with per-packet
+ * rx counters (the false-sharing line), a second line has packet-path
+ * private tx and congestion control counters, and a third the connection
+ * config.
+ *
+ * 'perf mem record' of this workload followed by 'perf report -s type'
+ * (see tests/shell/data_type_profiling.sh) resolves the accesses to
+ * struct net_conn members, showing the rx counters and the read-mostly
+ * identity sharing cacheline 0.
+ */
+#include <pthread.h>
+#include <sched.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <signal.h>
+#include <unistd.h>
+#include <linux/compiler.h>
+#include "../tests.h"
+
+struct net_conn {
+ /* cacheline 0: identity (read-mostly) + rx counters (per packet) */
+ uint32_t saddr; /* 0 */
+ uint32_t daddr; /* 4 */
+ uint16_t sport; /* 8 */
+ uint16_t dport; /* 10 */
+ uint8_t state; /* 12: 1 == ESTABLISHED */
+ uint8_t protocol; /* 13: 6 == TCP */
+ uint16_t __pad0; /* 14 */
+ uint64_t bytes_rx; /* 16: every packet */
+ uint64_t packets_rx; /* 24: every packet */
+ uint32_t rx_queue; /* 32: backlog depth, fluctuates */
+ uint8_t __pad1[24]; /* 36..59 */
+ uint32_t last_ack; /* 60: written per ACK */
+ /* cacheline 1: tx + congestion control (packet-path private) */
+ uint64_t bytes_tx; /* 64: every packet */
+ uint64_t packets_tx; /* 72: every packet */
+ uint32_t cwnd; /* 80: on every ACK */
+ uint32_t ssthresh; /* 84: on loss */
+ uint32_t rtt_us; /* 88: on every ACK */
+ uint32_t retrans; /* 92: on timeout */
+ uint32_t __pad2[8]; /* 96..127 */
+ /* cacheline 2: config, set at setup, read by everybody */
+ uint16_t mss; /* 128 */
+ uint8_t snd_wscale; /* 130 */
+ uint8_t rcv_wscale; /* 131 */
+ uint32_t keepalive_int; /* 132 */
+ uint32_t mark; /* 136: firewall mark */
+ uint32_t priority; /* 140: traffic class */
+ uint32_t __pad3[12]; /* 144..191 */
+} __attribute__((aligned(64)));
+
+/* Volatile so every iteration really loads and stores. */
+static volatile struct net_conn conn;
+/* Keeps the reader checksums alive after the threads join. */
+static volatile unsigned long fs_sink;
+
+static volatile sig_atomic_t done;
+
+/*
+ * One cacheline each: sum before cpu, or the implicit padding after cpu
+ * pushes the struct past 64 bytes, and aligning it to a cacheline then
+ * rounds it up to 128.
+ */
+struct fs_reader {
+ pthread_t thread;
+ unsigned long sum;
+ int cpu;
+ char __pad[64 - sizeof(pthread_t) - sizeof(unsigned long) - sizeof(int)];
+} __attribute__((aligned(64)));
+
+static void sighandler(int sig __maybe_unused)
+{
+ done = 1;
+}
+
+static void pin_to_cpu(int cpu)
+{
+ cpu_set_t set;
+
+ /* There may be no second CPU in a restricted cpuset. */
+ if (cpu < 0)
+ return;
+
+ CPU_ZERO(&set);
+ CPU_SET(cpu, &set);
+ /* Best effort: in a restricted cpuset this fails and the thread runs unpinned. */
+ pthread_setaffinity_np(pthread_self(), sizeof(set), &set);
+}
+
+/*
+ * Connection lookup, as a load balancer or 'ss' scrape would do it: the
+ * reads go straight to the global, this file is built -O0 and a local
+ * pointer would be reloaded from a stack slot, a form the data type
+ * resolver does not track.
+ */
+static void *reader_fn(void *arg)
+{
+ struct fs_reader *r = arg;
+ unsigned long sum = 0;
+
+ pthread_setname_np(pthread_self(), "fs-reader");
+ pin_to_cpu(r->cpu);
+
+ while (!done) {
+ sum += conn.saddr + conn.daddr + conn.sport + conn.dport +
+ conn.state + conn.protocol;
+ sum += conn.mss + conn.snd_wscale + conn.rcv_wscale +
+ conn.keepalive_int + conn.mark + conn.priority;
+ }
+ r->sum = sum;
+ return NULL;
+}
+
+static int false_sharing(int argc, const char **argv)
+{
+ double sec = 2.0;
+ int nreaders = 0, nr_allowed = 0, err = 1;
+ int *allowed = NULL, nallowed = 0;
+ cpu_set_t set;
+ int nr_mask_bits = sizeof(set) * 8 < CPU_SETSIZE ? sizeof(set) * 8 : CPU_SETSIZE;
+ struct fs_reader *readers = NULL;
+ int i, writer_cpu;
+ unsigned long n = 0;
+
+ pthread_setname_np(pthread_self(), "fs-writer");
+ if (argc > 0)
+ sec = atof(argv[0]);
+ if (!(sec > 0.0)) {
+ fprintf(stderr, "Error: seconds (%f) must be > 0\n", sec);
+ return 1;
+ }
+ if (argc > 1)
+ nreaders = atoi(argv[1]);
+
+ /*
+ * A connection that just got established: identity and config fixed
+ * from here on, counters at zero.
+ */
+ conn.saddr = 0x0a000001; /* 10.0.0.1 */
+ conn.daddr = 0x0a000002; /* 10.0.0.2 */
+ conn.sport = 54321;
+ conn.dport = 443;
+ conn.state = 1; /* ESTABLISHED */
+ conn.protocol = 6; /* TCP */
+ conn.mss = 1448;
+ conn.snd_wscale = 7;
+ conn.rcv_wscale = 7;
+ conn.keepalive_int = 7200;
+ conn.cwnd = 10;
+ conn.ssthresh = 65535;
+ conn.rtt_us = 50;
+
+ /*
+ * Pin against the allowed set, restricted cpusets still spread the threads.
+ * The whole mask is looked at, not the CPU count: the count can be lower
+ * than the highest ID in it, as when a cpuset allows only high numbered
+ * CPUs, and then no allowed CPU would be found at all.
+ */
+ if (sched_getaffinity(0, sizeof(set), &set) == 0) {
+ for (i = 0; i < nr_mask_bits; i++) {
+ if (!CPU_ISSET(i, &set))
+ continue;
+ nr_allowed++;
+ }
+ allowed = malloc(nr_allowed * sizeof(int));
+ if (allowed == NULL) {
+ fprintf(stderr, "Error: malloc failed for CPU list\n");
+ return 1;
+ }
+ for (i = 0; i < nr_mask_bits; i++) {
+ if (CPU_ISSET(i, &set))
+ allowed[nallowed++] = i;
+ }
+ }
+ if (nreaders <= 0) {
+ /* By default leave one CPU for the packet path, up to 4 readers. */
+ nreaders = nallowed > 1 ? nallowed - 1 : 1;
+ if (nreaders > 4)
+ nreaders = 4;
+ }
+
+ signal(SIGINT, sighandler);
+ signal(SIGALRM, sighandler);
+
+ readers = calloc(nreaders, sizeof(*readers));
+ if (readers == NULL) {
+ fprintf(stderr, "Error: calloc failed for %d readers\n", nreaders);
+ goto out;
+ }
+ for (i = 0; i < nreaders; i++) {
+ int cpu = nallowed > 1 ? allowed[(i + 1) % nallowed] : -1;
+
+ readers[i].cpu = cpu;
+ if (pthread_create(&readers[i].thread, NULL, reader_fn, &readers[i])) {
+ fprintf(stderr, "Error: failed to create reader %d\n", i);
+ done = 1; // Ensure started threads terminate.
+ nreaders = i;
+ goto out_join;
+ }
+ }
+ writer_cpu = nallowed > 0 ? allowed[0] : -1;
+ if (nallowed == 1)
+ fprintf(stderr, "Warning: single CPU allowed, no cross-CPU traffic expected\n");
+ if (writer_cpu >= 0)
+ pin_to_cpu(writer_cpu);
+
+ /*
+ * The packet path: receive, acknowledge, transmit, repeat; every 64th
+ * packet simulates a loss so ssthresh/retrans get sampled too.
+ */
+ if (sec < 1.0) {
+ useconds_t usecs = (useconds_t)(sec * 1000000.0);
+
+ ualarm(usecs > 0 ? usecs : 1, 0);
+ } else
+ alarm((unsigned int)sec);
+ while (!done) {
+ conn.bytes_rx += conn.mss;
+ conn.packets_rx++;
+ conn.rx_queue = (uint32_t)(n & 0x3f);
+ conn.last_ack = (uint32_t)n;
+ conn.bytes_tx += conn.mss;
+ conn.packets_tx++;
+ conn.cwnd = 10 + (n & 15);
+ conn.rtt_us = 50 + (n & 7);
+ if ((n & 63) == 0) {
+ conn.ssthresh = conn.cwnd / 2;
+ conn.retrans++;
+ }
+ n++;
+ }
+ err = 0;
+out_join:
+ for (i = 0; i < nreaders; i++) {
+ if (readers[i].thread) {
+ pthread_join(readers[i].thread, /*retval=*/NULL);
+ fs_sink += readers[i].sum;
+ }
+ }
+ fs_sink += (unsigned long)(conn.bytes_rx + conn.bytes_tx + n);
+ free(readers);
+out:
+ free(allowed);
+ return err;
+}
+
+DEFINE_WORKLOAD(false_sharing);
--
2.55.0
^ permalink raw reply [flat|nested] 10+ messages in thread