Re: [PATCH] perf ftrace: Use process/session specific trace settings

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* Re: [PATCH] perf ftrace: Use process/session specific trace settings
       [not found] <20250516131023.357458-1-tmricht@linux.ibm.com>
@ 2025-05-16 18:52 ` Arnaldo Carvalho de Melo
  2025-05-16 19:09   ` Arnaldo Carvalho de Melo
  0 siblings, 1 reply; 3+ messages in thread
From: Arnaldo Carvalho de Melo @ 2025-05-16 18:52 UTC (permalink / raw)
  To: Thomas Richter
  Cc: linux390-list, sumanthk, hca, agordeev, gor, Alexander Egorenkov,
	linux-perf-users, Linux Kernel Mailing List

On Fri, May 16, 2025 at 03:10:23PM +0200, Thomas Richter wrote:
> Executing perf ftrace commands ftrace, profile and latency
> leave tracing disabled as can seen in this output:

You forgot to CC lkml and linux-perf-users mailing list, I'm doing it
now, noticed when b4 didn't manage to find it.

Thanks for working on this! From a quick glance it looks great, I'm
testing it now.

- Arnaldo
 
>  # echo 1 > /sys/kernel/debug/tracing/tracing_on
>  # cat /sys/kernel/debug/tracing/tracing_on
>  1
>  # perf ftrace trace --graph-opts depth=5 sleep 0.1 > /dev/null
>  # cat /sys/kernel/debug/tracing/tracing_on
>  0
>  #
> 
> The tracing_on file is not restored to its value before the command.
> Fix this behavior and restore the trace setting to what
> is was before the invocation of the command.
> On Fedora 41 and 42 tracing is turned on by default.
> 
> This patch use the .../tracing/instances/XXX subdirectory feature.
> Each perf ftrace invocation creates its own session/process
> specific subdirectory and does not change the global state
> in the .../tracing directory itself.
> 
> Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
> Suggested-by: Arnaldo Carvalho de Melo <acme@kernel.org>
> Reported-by: Alexander Egorenkov <egorenar@linux.ibm.com>
> ---
>  tools/perf/builtin-ftrace.c | 79 ++++++++++++++++++++++++++++++++++---
>  1 file changed, 73 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index 7caa18d5ffc3..f523039c585f 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -38,6 +38,8 @@
>  #include "util/units.h"
>  #include "util/parse-sublevel-options.h"
>  
> +#include <sys/stat.h>
> +
>  #define DEFAULT_TRACER  "function_graph"
>  
>  static volatile sig_atomic_t workload_exec_errno;
> @@ -45,6 +47,8 @@ static volatile sig_atomic_t done;
>  
>  static struct stats latency_stats;  /* for tracepoints */
>  
> +static char tracing_instance[PATH_MAX];	/* Trace instance directory */
> +
>  static void sig_handler(int sig __maybe_unused)
>  {
>  	done = true;
> @@ -100,6 +104,34 @@ static bool is_ftrace_supported(void)
>  	return supported;
>  }
>  
> +/*
> + * Wrapper to test if a file in directory .../tracing/instances/XXX
> + * exists. If so return the .../tracing/instances/XXX file for use.
> + * Otherwise the file exists only in directory .../tracing and
> + * is applicable to all instances, for example file available_filter_functions.
> + * Return that file name in this case.
> + *
> + * This functions works similar to get_tracing_file() and expects its caller
> + * to free the returned file name.
> + *
> + * The global variable tracing_instance is set in init_tracing_instance()
> + * called a the  beginning to a process specific tracing subdirectory.
> + */
> +static char *get_tracing_instance_file(const char *name)
> +{
> +	char *file;
> +
> +	if (asprintf(&file, "%s/%s", tracing_instance, name) < 0)
> +		return NULL;
> +
> +	if (!access(file, F_OK))
> +		return file;
> +
> +	put_tracing_file(file);
> +	file = get_tracing_file(name);
> +	return file;
> +}
> +
>  static int __write_tracing_file(const char *name, const char *val, bool append)
>  {
>  	char *file;
> @@ -109,7 +141,7 @@ static int __write_tracing_file(const char *name, const char *val, bool append)
>  	char errbuf[512];
>  	char *val_copy;
>  
> -	file = get_tracing_file(name);
> +	file = get_tracing_instance_file(name);
>  	if (!file) {
>  		pr_debug("cannot get tracing file: %s\n", name);
>  		return -1;
> @@ -167,7 +199,7 @@ static int read_tracing_file_to_stdout(const char *name)
>  	int fd;
>  	int ret = -1;
>  
> -	file = get_tracing_file(name);
> +	file = get_tracing_instance_file(name);
>  	if (!file) {
>  		pr_debug("cannot get tracing file: %s\n", name);
>  		return -1;
> @@ -209,7 +241,7 @@ static int read_tracing_file_by_line(const char *name,
>  	char *file;
>  	FILE *fp;
>  
> -	file = get_tracing_file(name);
> +	file = get_tracing_instance_file(name);
>  	if (!file) {
>  		pr_debug("cannot get tracing file: %s\n", name);
>  		return -1;
> @@ -299,6 +331,36 @@ static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
>  	return 0;
>  }
>  
> +/* Remove .../tracing/instances/XXX subdirectory created with
> + * init_tracing_instance().
> + */
> +static void exit_tracing_instance(void)
> +{
> +	rmdir(tracing_instance);
> +}
> +
> +/* Create subdirectory within .../tracing/instances/XXX to have session
> + * or process specific setup. To delete this setup, simply remove the
> + * subdirectory.
> + */
> +static int init_tracing_instance(void)
> +{
> +	char dirname[] = "instances/perf-ftrace-XXXXXX";
> +	char *path;
> +
> +	path = get_tracing_file(dirname);
> +	if (!path)
> +		return -1;
> +	strcpy(tracing_instance, path);
> +	put_tracing_file(path);
> +	path = mkdtemp(tracing_instance);
> +	if (!path) {
> +		pr_err("failed to create tracing/instances directory\n");
> +		return -1;
> +	}
> +	return 0;
> +}
> +
>  static int set_tracing_pid(struct perf_ftrace *ftrace)
>  {
>  	int i;
> @@ -648,7 +710,7 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace)
>  
>  	setup_pager();
>  
> -	trace_file = get_tracing_file("trace_pipe");
> +	trace_file = get_tracing_instance_file("trace_pipe");
>  	if (!trace_file) {
>  		pr_err("failed to open trace_pipe\n");
>  		goto out_reset;
> @@ -942,7 +1004,7 @@ static int prepare_func_latency(struct perf_ftrace *ftrace)
>  		return -1;
>  	}
>  
> -	trace_file = get_tracing_file("trace_pipe");
> +	trace_file = get_tracing_instance_file("trace_pipe");
>  	if (!trace_file) {
>  		pr_err("failed to open trace_pipe\n");
>  		return -1;
> @@ -1323,7 +1385,7 @@ static int __cmd_profile(struct perf_ftrace *ftrace)
>  
>  	setup_pager();
>  
> -	trace_file = get_tracing_file("trace_pipe");
> +	trace_file = get_tracing_instance_file("trace_pipe");
>  	if (!trace_file) {
>  		pr_err("failed to open trace_pipe\n");
>  		goto out_reset;
> @@ -1740,6 +1802,9 @@ int cmd_ftrace(int argc, const char **argv)
>  	if (!argc && target__none(&ftrace.target))
>  		ftrace.target.system_wide = true;
>  
> +	if (init_tracing_instance())
> +		goto out_delete_filters;
> +
>  	switch (subcmd) {
>  	case PERF_FTRACE_TRACE:
>  		cmd_func = __cmd_ftrace;
> @@ -1839,5 +1904,7 @@ int cmd_ftrace(int argc, const char **argv)
>  	delete_filter_func(&ftrace.graph_funcs);
>  	delete_filter_func(&ftrace.nograph_funcs);
>  
> +	exit_tracing_instance();
> +
>  	return ret;
>  }
> -- 
> 2.49.0

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] perf ftrace: Use process/session specific trace settings
  2025-05-16 18:52 ` [PATCH] perf ftrace: Use process/session specific trace settings Arnaldo Carvalho de Melo
@ 2025-05-16 19:09   ` Arnaldo Carvalho de Melo
  2025-05-16 22:43     ` Steven Rostedt
  0 siblings, 1 reply; 3+ messages in thread
From: Arnaldo Carvalho de Melo @ 2025-05-16 19:09 UTC (permalink / raw)
  To: Thomas Richter
  Cc: linux390-list, sumanthk, hca, agordeev, gor, Alexander Egorenkov,
	Steven Rostedt, linux-perf-users, Linux Kernel Mailing List

CCing Steven,

On Fri, May 16, 2025 at 03:52:38PM -0300, Arnaldo Carvalho de Melo wrote:
> On Fri, May 16, 2025 at 03:10:23PM +0200, Thomas Richter wrote:
> > Executing perf ftrace commands ftrace, profile and latency
> > leave tracing disabled as can seen in this output:
> 
> You forgot to CC lkml and linux-perf-users mailing list, I'm doing it
> now, noticed when b4 didn't manage to find it.
> 
> Thanks for working on this! From a quick glance it looks great, I'm
> testing it now.

So, you create the instance, configure it, and at the end you do a rmdir
that will trow it away, since we don't need it anymore, but then you're
writing to its tunables right before trowing it away, i.e. restoring
previous values? I think you can remove that when using instances,
right?

For instance, at the start you do:

openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-gWVKWs/tracing_on", O_WRONLY|O_TRUNC) = 4
write(4, "1\n", 2) 

And then at the end:

openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-gWVKWs/tracing_on", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2) 

Is that a requirement for "tracing_on", could we do away with that, i.e.
a rmdir would implicitely stop tracing on that instance?

Lemme check:

root@number:~# mkdir /sys/kernel/tracing/instances/perf-ftrace-LX75Yk
root@number:~# echo function_graph > /sys/kernel/tracing/instances/perf-ftrace-LX75Yk/current_tracer 
root@number:~# head -5 /sys/kernel/tracing/instances/perf-ftrace-LX75Yk/trace
# tracer: function_graph
#
# CPU  DURATION                  FUNCTION CALLS
# |     |   |                     |   |   |   |
  6)   1.924 us    |                        } /* enqueue_entity */
root@number:~# head -10 /sys/kernel/tracing/instances/perf-ftrace-LX75Yk/trace
# tracer: function_graph
#
# CPU  DURATION                  FUNCTION CALLS
# |     |   |                     |   |   |   |
 18)   0.140 us    |                            } /* get_nohz_timer_target */
 18)   0.060 us    |                            enqueue_hrtimer();
 18)   0.041 us    |                            _raw_spin_unlock_irqrestore();
 18)   0.632 us    |                          } /* hrtimer_start_range_ns */
 18)   0.802 us    |                        } /* task_non_contending */
 18)               |                        hrtimer_try_to_cancel() {
root@number:~# head -10 /sys/kernel/tracing/instances/perf-ftrace-LX75Yk/trace
# tracer: function_graph
#
# CPU  DURATION                  FUNCTION CALLS
# |     |   |                     |   |   |   |
 17)   0.090 us    |                  __update_load_avg_se();
 17)   0.051 us    |                  __update_load_avg_cfs_rq();
 17)               |                  update_cfs_group() {
 17)   0.050 us    |                    reweight_entity();
 17)   0.260 us    |                  }
 17)               |                  place_entity() {
root@number:~# rmdir /sys/kernel/tracing/instances/perf-ftrace-LX75Yk
root@number:~# ls -la /sys/kernel/tracing/instances/perf-ftrace-LX75Yk
ls: cannot access '/sys/kernel/tracing/instances/perf-ftrace-LX75Yk': No such file or directory
root@number:~#

Yeah, you can just call rmdir and be done with it :-)

- Arnaldo

mkdir("/sys/kernel/tracing/instances/perf-ftrace-LX75Yk", 0700) = 0
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/tracing_on", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/current_tracer", O_WRONLY|O_TRUNC) = 3
write(3, "nop\n", 4)                    = 4
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/set_ftrace_pid", O_WRONLY|O_TRUNC) = 3
write(3, " \n", 2)                      = 2
openat(AT_FDCWD, "/sys/devices/system/cpu/online", O_RDONLY) = 3
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/tracing_cpumask", O_WRONLY|O_TRUNC) = 3
write(3, "ffffffff\n", 9)               = 9
openat(AT_FDCWD, "/sys/kernel/tracing/max_graph_depth", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/tracing_thresh", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/set_ftrace_filter", O_WRONLY|O_TRUNC) = 3
write(3, " \n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/set_ftrace_notrace", O_WRONLY|O_TRUNC) = 3
write(3, " \n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/set_graph_function", O_WRONLY|O_TRUNC) = 3
write(3, " \n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/set_graph_notrace", O_WRONLY|O_TRUNC) = 3
write(3, " \n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/function-fork", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/func_stack_trace", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/sleep-time", O_WRONLY|O_TRUNC) = 3
write(3, "1\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/funcgraph-irqs", O_WRONLY|O_TRUNC) = 3
write(3, "1\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/funcgraph-proc", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/funcgraph-abstime", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/funcgraph-tail", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/latency-format", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/irq-info", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/trace", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/set_ftrace_pid", O_WRONLY|O_APPEND) = 3
write(3, "1277499\n", 8)                = 8
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/set_ftrace_filter", O_WRONLY|O_APPEND) = 3
write(3, "schedule\n", 9)               = 9
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/current_tracer", O_WRONLY|O_TRUNC) = 3
write(3, "function_graph\n", 15)        = 15
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/trace_pipe", O_RDONLY) = 3
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/tracing_on", O_WRONLY|O_TRUNC) = 4
write(4, "1\n", 2)                      = 2
write(6, "\0", 1)                       = 1
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=1277499, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/tracing_on", O_WRONLY|O_TRUNC) = 4
write(4, "0\n", 2)                      = 2
write(1, "#   DURATION     |      COUNT | "..., 81#   DURATION     |      COUNT | GRAPH                                          |
) = 81
write(1, "     0 -    1 us |          0 | "..., 81     0 -    1 us |          0 |                                                |
) = 81
write(1, "     1 -    2 us |          0 | "..., 81     1 -    2 us |          0 |                                                |
) = 81
write(1, "     2 -    4 us |          0 | "..., 81     2 -    4 us |          0 |                                                |
) = 81
write(1, "     4 -    8 us |          0 | "..., 81     4 -    8 us |          0 |                                                |
) = 81
write(1, "     8 -   16 us |          0 | "..., 81     8 -   16 us |          0 |                                                |
) = 81
write(1, "    16 -   32 us |          0 | "..., 81    16 -   32 us |          0 |                                                |
) = 81
write(1, "    32 -   64 us |          0 | "..., 81    32 -   64 us |          0 |                                                |
) = 81
write(1, "    64 -  128 us |          0 | "..., 81    64 -  128 us |          0 |                                                |
) = 81
write(1, "   128 -  256 us |          0 | "..., 81   128 -  256 us |          0 |                                                |
) = 81
write(1, "   256 -  512 us |          0 | "..., 81   256 -  512 us |          0 |                                                |
) = 81
write(1, "   512 - 1024 us |          0 | "..., 81   512 - 1024 us |          0 |                                                |
) = 81
write(1, "     1 -    2 ms |          0 | "..., 81     1 -    2 ms |          0 |                                                |
) = 81
write(1, "     2 -    4 ms |          0 | "..., 81     2 -    4 ms |          0 |                                                |
) = 81
write(1, "     4 -    8 ms |          0 | "..., 81     4 -    8 ms |          0 |                                                |
) = 81
write(1, "     8 -   16 ms |          0 | "..., 81     8 -   16 ms |          0 |                                                |
) = 81
write(1, "    16 -   32 ms |          0 | "..., 81    16 -   32 ms |          0 |                                                |
) = 81
write(1, "    32 -   64 ms |          0 | "..., 81    32 -   64 ms |          0 |                                                |
) = 81
write(1, "    64 -  128 ms |          0 | "..., 81    64 -  128 ms |          0 |                                                |
) = 81
write(1, "   128 -  256 ms |          0 | "..., 81   128 -  256 ms |          0 |                                                |
) = 81
write(1, "   256 -  512 ms |          1 | "..., 81   256 -  512 ms |          1 | ############################################## |
) = 81
write(1, "   512 - 1024 ms |          0 | "..., 81   512 - 1024 ms |          0 |                                                |
) = 81
write(1, "     1 - ...  s  |          0 | "..., 81     1 - ...  s  |          0 |                                                |
) = 81
write(1, "\n# statistics  (in usec)\n", 25
# statistics  (in usec)
) = 25
write(1, "  total time:              10000"..., 35  total time:              1000044
) = 35
write(1, "    avg time:              10000"..., 35    avg time:              1000044
) = 35
write(1, "    max time:              10000"..., 35    max time:              1000044
) = 35
write(1, "    min time:              10000"..., 35    min time:              1000044
) = 35
write(1, "       count:                   "..., 35       count:                    1
) = 35
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/tracing_on", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/current_tracer", O_WRONLY|O_TRUNC) = 3
write(3, "nop\n", 4)                    = 4
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/set_ftrace_pid", O_WRONLY|O_TRUNC) = 3
write(3, " \n", 2)                      = 2
openat(AT_FDCWD, "/sys/devices/system/cpu/online", O_RDONLY) = 3
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/tracing_cpumask", O_WRONLY|O_TRUNC) = 3
write(3, "ffffffff\n", 9)               = 9
openat(AT_FDCWD, "/sys/kernel/tracing/max_graph_depth", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/tracing_thresh", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/set_ftrace_filter", O_WRONLY|O_TRUNC) = 3
write(3, " \n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/set_ftrace_notrace", O_WRONLY|O_TRUNC) = 3
write(3, " \n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/set_graph_function", O_WRONLY|O_TRUNC) = 3
write(3, " \n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/set_graph_notrace", O_WRONLY|O_TRUNC) = 3
write(3, " \n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/function-fork", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/func_stack_trace", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/sleep-time", O_WRONLY|O_TRUNC) = 3
write(3, "1\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/funcgraph-irqs", O_WRONLY|O_TRUNC) = 3
write(3, "1\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/funcgraph-proc", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/funcgraph-abstime", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/funcgraph-tail", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/latency-format", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
openat(AT_FDCWD, "/sys/kernel/tracing/instances/perf-ftrace-LX75Yk/options/irq-info", O_WRONLY|O_TRUNC) = 3
write(3, "0\n", 2)                      = 2
rmdir("/sys/kernel/tracing/instances/perf-ftrace-LX75Yk") = 0
+++ exited with 0 +++
root@number:~# 

> >  # echo 1 > /sys/kernel/debug/tracing/tracing_on
> >  # cat /sys/kernel/debug/tracing/tracing_on
> >  1
> >  # perf ftrace trace --graph-opts depth=5 sleep 0.1 > /dev/null
> >  # cat /sys/kernel/debug/tracing/tracing_on
> >  0
> >  #
> > 
> > The tracing_on file is not restored to its value before the command.
> > Fix this behavior and restore the trace setting to what
> > is was before the invocation of the command.
> > On Fedora 41 and 42 tracing is turned on by default.
> > 
> > This patch use the .../tracing/instances/XXX subdirectory feature.
> > Each perf ftrace invocation creates its own session/process
> > specific subdirectory and does not change the global state
> > in the .../tracing directory itself.
> > 
> > Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
> > Suggested-by: Arnaldo Carvalho de Melo <acme@kernel.org>
> > Reported-by: Alexander Egorenkov <egorenar@linux.ibm.com>
> > ---
> >  tools/perf/builtin-ftrace.c | 79 ++++++++++++++++++++++++++++++++++---
> >  1 file changed, 73 insertions(+), 6 deletions(-)
> > 
> > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> > index 7caa18d5ffc3..f523039c585f 100644
> > --- a/tools/perf/builtin-ftrace.c
> > +++ b/tools/perf/builtin-ftrace.c
> > @@ -38,6 +38,8 @@
> >  #include "util/units.h"
> >  #include "util/parse-sublevel-options.h"
> >  
> > +#include <sys/stat.h>
> > +
> >  #define DEFAULT_TRACER  "function_graph"
> >  
> >  static volatile sig_atomic_t workload_exec_errno;
> > @@ -45,6 +47,8 @@ static volatile sig_atomic_t done;
> >  
> >  static struct stats latency_stats;  /* for tracepoints */
> >  
> > +static char tracing_instance[PATH_MAX];	/* Trace instance directory */
> > +
> >  static void sig_handler(int sig __maybe_unused)
> >  {
> >  	done = true;
> > @@ -100,6 +104,34 @@ static bool is_ftrace_supported(void)
> >  	return supported;
> >  }
> >  
> > +/*
> > + * Wrapper to test if a file in directory .../tracing/instances/XXX
> > + * exists. If so return the .../tracing/instances/XXX file for use.
> > + * Otherwise the file exists only in directory .../tracing and
> > + * is applicable to all instances, for example file available_filter_functions.
> > + * Return that file name in this case.
> > + *
> > + * This functions works similar to get_tracing_file() and expects its caller
> > + * to free the returned file name.
> > + *
> > + * The global variable tracing_instance is set in init_tracing_instance()
> > + * called a the  beginning to a process specific tracing subdirectory.
> > + */
> > +static char *get_tracing_instance_file(const char *name)
> > +{
> > +	char *file;
> > +
> > +	if (asprintf(&file, "%s/%s", tracing_instance, name) < 0)
> > +		return NULL;
> > +
> > +	if (!access(file, F_OK))
> > +		return file;
> > +
> > +	put_tracing_file(file);
> > +	file = get_tracing_file(name);
> > +	return file;
> > +}
> > +
> >  static int __write_tracing_file(const char *name, const char *val, bool append)
> >  {
> >  	char *file;
> > @@ -109,7 +141,7 @@ static int __write_tracing_file(const char *name, const char *val, bool append)
> >  	char errbuf[512];
> >  	char *val_copy;
> >  
> > -	file = get_tracing_file(name);
> > +	file = get_tracing_instance_file(name);
> >  	if (!file) {
> >  		pr_debug("cannot get tracing file: %s\n", name);
> >  		return -1;
> > @@ -167,7 +199,7 @@ static int read_tracing_file_to_stdout(const char *name)
> >  	int fd;
> >  	int ret = -1;
> >  
> > -	file = get_tracing_file(name);
> > +	file = get_tracing_instance_file(name);
> >  	if (!file) {
> >  		pr_debug("cannot get tracing file: %s\n", name);
> >  		return -1;
> > @@ -209,7 +241,7 @@ static int read_tracing_file_by_line(const char *name,
> >  	char *file;
> >  	FILE *fp;
> >  
> > -	file = get_tracing_file(name);
> > +	file = get_tracing_instance_file(name);
> >  	if (!file) {
> >  		pr_debug("cannot get tracing file: %s\n", name);
> >  		return -1;
> > @@ -299,6 +331,36 @@ static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
> >  	return 0;
> >  }
> >  
> > +/* Remove .../tracing/instances/XXX subdirectory created with
> > + * init_tracing_instance().
> > + */
> > +static void exit_tracing_instance(void)
> > +{
> > +	rmdir(tracing_instance);
> > +}
> > +
> > +/* Create subdirectory within .../tracing/instances/XXX to have session
> > + * or process specific setup. To delete this setup, simply remove the
> > + * subdirectory.
> > + */
> > +static int init_tracing_instance(void)
> > +{
> > +	char dirname[] = "instances/perf-ftrace-XXXXXX";
> > +	char *path;
> > +
> > +	path = get_tracing_file(dirname);
> > +	if (!path)
> > +		return -1;
> > +	strcpy(tracing_instance, path);
> > +	put_tracing_file(path);
> > +	path = mkdtemp(tracing_instance);
> > +	if (!path) {
> > +		pr_err("failed to create tracing/instances directory\n");
> > +		return -1;
> > +	}
> > +	return 0;
> > +}
> > +
> >  static int set_tracing_pid(struct perf_ftrace *ftrace)
> >  {
> >  	int i;
> > @@ -648,7 +710,7 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace)
> >  
> >  	setup_pager();
> >  
> > -	trace_file = get_tracing_file("trace_pipe");
> > +	trace_file = get_tracing_instance_file("trace_pipe");
> >  	if (!trace_file) {
> >  		pr_err("failed to open trace_pipe\n");
> >  		goto out_reset;
> > @@ -942,7 +1004,7 @@ static int prepare_func_latency(struct perf_ftrace *ftrace)
> >  		return -1;
> >  	}
> >  
> > -	trace_file = get_tracing_file("trace_pipe");
> > +	trace_file = get_tracing_instance_file("trace_pipe");
> >  	if (!trace_file) {
> >  		pr_err("failed to open trace_pipe\n");
> >  		return -1;
> > @@ -1323,7 +1385,7 @@ static int __cmd_profile(struct perf_ftrace *ftrace)
> >  
> >  	setup_pager();
> >  
> > -	trace_file = get_tracing_file("trace_pipe");
> > +	trace_file = get_tracing_instance_file("trace_pipe");
> >  	if (!trace_file) {
> >  		pr_err("failed to open trace_pipe\n");
> >  		goto out_reset;
> > @@ -1740,6 +1802,9 @@ int cmd_ftrace(int argc, const char **argv)
> >  	if (!argc && target__none(&ftrace.target))
> >  		ftrace.target.system_wide = true;
> >  
> > +	if (init_tracing_instance())
> > +		goto out_delete_filters;
> > +
> >  	switch (subcmd) {
> >  	case PERF_FTRACE_TRACE:
> >  		cmd_func = __cmd_ftrace;
> > @@ -1839,5 +1904,7 @@ int cmd_ftrace(int argc, const char **argv)
> >  	delete_filter_func(&ftrace.graph_funcs);
> >  	delete_filter_func(&ftrace.nograph_funcs);
> >  
> > +	exit_tracing_instance();
> > +
> >  	return ret;
> >  }
> > -- 
> > 2.49.0

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] perf ftrace: Use process/session specific trace settings
  2025-05-16 19:09   ` Arnaldo Carvalho de Melo
@ 2025-05-16 22:43     ` Steven Rostedt
  0 siblings, 0 replies; 3+ messages in thread
From: Steven Rostedt @ 2025-05-16 22:43 UTC (permalink / raw)
  To: Arnaldo Carvalho de Melo
  Cc: Thomas Richter, linux390-list, sumanthk, hca, agordeev, gor,
	Alexander Egorenkov, linux-perf-users, Linux Kernel Mailing List

On Fri, 16 May 2025 16:09:57 -0300
Arnaldo Carvalho de Melo <acme@kernel.org> wrote:

> Yeah, you can just call rmdir and be done with it :-)

Yes. Removing an instance should reset everything about it before it
removes it. It disables events and sets the current tracer to "nop"
(stopping function tracing and such if it was present).

If there's a file open, then the rmdir should fail with -EBUSY.

-- Steve

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2025-05-16 22:43 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
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2025-05-16 18:52 ` [PATCH] perf ftrace: Use process/session specific trace settings Arnaldo Carvalho de Melo
2025-05-16 19:09   ` Arnaldo Carvalho de Melo
2025-05-16 22:43     ` Steven Rostedt

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