[PATCH] Enable the enable_on_exec flag if record forks the target

[PATCH] Enable the enable_on_exec flag if record forks the target

[Eric B Munson]

When forking its target, perf record can capture data from before the target
application is started.  Perf stat uses the enable_on_exec flag in the event
attributes to keep from displaying events from before the target program
starts, this patch adds the same functionality to perf record when it is will
fork the target process.

Signed-off-by: Eric B Munson <ebmunson@us.ibm.com>
---
 tools/perf/builtin-record.c |   13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 771533c..625076e 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -224,7 +224,7 @@ static struct perf_header_attr *get_header_attr(struct perf_event_attr *a, int n
 	return h_attr;
 }
 
-static void create_counter(int counter, int cpu, pid_t pid)
+static void create_counter(int counter, int cpu, pid_t pid, bool forks)
 {
 	char *filter = filters[counter];
 	struct perf_event_attr *attr = attrs + counter;
@@ -273,6 +273,9 @@ static void create_counter(int counter, int cpu, pid_t pid)
 	attr->inherit		= inherit;
 	attr->disabled		= 1;
 
+	if (forks)
+		attr->enable_on_exec = 1;
+
 try_again:
 	fd[nr_cpu][counter] = sys_perf_event_open(attr, pid, cpu, group_fd, 0);
 
@@ -376,13 +379,13 @@ try_again:
 	ioctl(fd[nr_cpu][counter], PERF_EVENT_IOC_ENABLE);
 }
 
-static void open_counters(int cpu, pid_t pid)
+static void open_counters(int cpu, pid_t pid, bool forks)
 {
 	int counter;
 
 	group_fd = -1;
 	for (counter = 0; counter < nr_counters; counter++)
-		create_counter(counter, cpu, pid);
+		create_counter(counter, cpu, pid, forks);
 
 	nr_cpu++;
 }
@@ -542,10 +545,10 @@ static int __cmd_record(int argc, const char **argv)
 
 
 	if ((!system_wide && !inherit) || profile_cpu != -1) {
-		open_counters(profile_cpu, target_pid);
+		open_counters(profile_cpu, target_pid, forks);
 	} else {
 		for (i = 0; i < nr_cpus; i++)
-			open_counters(i, target_pid);
+			open_counters(i, target_pid, forks);
 	}
 
 	if (file_new) {
-- 
1.6.3.3

Re: [PATCH] Enable the enable_on_exec flag if record forks the target

[Arnaldo Carvalho de Melo]

Em Wed, Mar 03, 2010 at 10:06:27PM +0000, Eric B Munson escreveu:
> When forking its target, perf record can capture data from before the target
> application is started.  Perf stat uses the enable_on_exec flag in the event
> attributes to keep from displaying events from before the target program
> starts, this patch adds the same functionality to perf record when it is will
> fork the target process.

Good catch, Dave, this will help that case too, or at least avoid
exercising that bug you fixed by flushing maps when a comm is received
:-)

Eric, I'll test your patches for handling multiple counters in 'perf
report'and integrate then, most likely tomorrow, thanks!

- Arnaldo

Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
 
> Signed-off-by: Eric B Munson <ebmunson@us.ibm.com>
> ---
>  tools/perf/builtin-record.c |   13 ++++++++-----
>  1 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 771533c..625076e 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -224,7 +224,7 @@ static struct perf_header_attr *get_header_attr(struct perf_event_attr *a, int n
>  	return h_attr;
>  }
>  
> -static void create_counter(int counter, int cpu, pid_t pid)
> +static void create_counter(int counter, int cpu, pid_t pid, bool forks)
>  {
>  	char *filter = filters[counter];
>  	struct perf_event_attr *attr = attrs + counter;
> @@ -273,6 +273,9 @@ static void create_counter(int counter, int cpu, pid_t pid)
>  	attr->inherit		= inherit;
>  	attr->disabled		= 1;
>  
> +	if (forks)
> +		attr->enable_on_exec = 1;
> +
>  try_again:
>  	fd[nr_cpu][counter] = sys_perf_event_open(attr, pid, cpu, group_fd, 0);
>  
> @@ -376,13 +379,13 @@ try_again:
>  	ioctl(fd[nr_cpu][counter], PERF_EVENT_IOC_ENABLE);
>  }
>  
> -static void open_counters(int cpu, pid_t pid)
> +static void open_counters(int cpu, pid_t pid, bool forks)
>  {
>  	int counter;
>  
>  	group_fd = -1;
>  	for (counter = 0; counter < nr_counters; counter++)
> -		create_counter(counter, cpu, pid);
> +		create_counter(counter, cpu, pid, forks);
>  
>  	nr_cpu++;
>  }
> @@ -542,10 +545,10 @@ static int __cmd_record(int argc, const char **argv)
>  
>  
>  	if ((!system_wide && !inherit) || profile_cpu != -1) {
> -		open_counters(profile_cpu, target_pid);
> +		open_counters(profile_cpu, target_pid, forks);
>  	} else {
>  		for (i = 0; i < nr_cpus; i++)
> -			open_counters(i, target_pid);
> +			open_counters(i, target_pid, forks);
>  	}
>  
>  	if (file_new) {
> -- 
> 1.6.3.3