Commit 46be604b authored by Zhang, Yanmin's avatar Zhang, Yanmin Committed by Ingo Molnar
Browse files

perf record: Enable counters only when kernel is execing subcommand 



'perf record' starts counters before subcommand is execed, so
the statistics is not precise because it includes data of some
preparation steps. I fix it with the patch.

In addition, change the condition to fork/exec subcommand. If
there is a subcommand parameter, perf always fork/exec it. The
usage example is:

 # perf record -f -a sleep 10

So this command could collect statistics for 10 seconds
precisely. User still could stop it by CTRL+C. Without the new
capability, user could only input CTRL+C to stop it without
precise time clock.

Signed-off-by: default avatarZhang Yanmin <yanmin_zhang@linux.intel.com>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sheng Yang <sheng@linux.intel.com>
Cc: oerg Roedel <joro@8bytes.org>
Cc: Jes Sorensen <Jes.Sorensen@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: <zhiteng.huang@intel.com>
Cc: Zachary Amsden <zamsden@redhat.com>
LKML-Reference: <1268922965-14774-2-git-send-email-acme@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 6be2850e

tools/perf/builtin-record.c

+15 −18
Original line number Diff line number Diff line
@@ -225,7 +225,7 @@ 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, bool forks)

static void create_counter(int counter, int cpu, pid_t pid)

{

	char *filter = filters[counter];

	struct perf_event_attr *attr = attrs + counter;
@@ -275,10 +275,10 @@ static void create_counter(int counter, int cpu, pid_t pid, bool forks) 
	attr->mmap		= track;

	attr->comm		= track;

	attr->inherit		= inherit;

	if (target_pid == -1 && !system_wide) {

		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);
@@ -380,17 +380,15 @@ try_again: 
			exit(-1);

		}

	}



	ioctl(fd[nr_cpu][counter], PERF_EVENT_IOC_ENABLE);

}



static void open_counters(int cpu, pid_t pid, bool forks)

static void open_counters(int cpu, pid_t pid)

{

	int counter;



	group_fd = -1;

	for (counter = 0; counter < nr_counters; counter++)

		create_counter(counter, cpu, pid, forks);

		create_counter(counter, cpu, pid);



	nr_cpu++;

}
@@ -425,7 +423,7 @@ static int __cmd_record(int argc, const char **argv) 
	int err;

	unsigned long waking = 0;

	int child_ready_pipe[2], go_pipe[2];

	const bool forks = target_pid == -1 && argc > 0;

	const bool forks = argc > 0;

	char buf;



	page_size = sysconf(_SC_PAGE_SIZE);
@@ -496,13 +494,13 @@ static int __cmd_record(int argc, const char **argv) 
	atexit(atexit_header);



	if (forks) {

		pid = fork();

		child_pid = fork();

		if (pid < 0) {

			perror("failed to fork");

			exit(-1);

		}



		if (!pid) {

		if (!child_pid) {

			close(child_ready_pipe[0]);

			close(go_pipe[1]);

			fcntl(go_pipe[0], F_SETFD, FD_CLOEXEC);
@@ -531,11 +529,6 @@ static int __cmd_record(int argc, const char **argv) 
			exit(-1);

		}



		child_pid = pid;



		if (!system_wide)

			target_pid = pid;



		close(child_ready_pipe[1]);

		close(go_pipe[0]);

		/*
@@ -548,13 +541,17 @@ static int __cmd_record(int argc, const char **argv) 
		close(child_ready_pipe[0]);

	}



	if (forks && target_pid == -1 && !system_wide)

		pid = child_pid;

	else

		pid = target_pid;



	if ((!system_wide && !inherit) || profile_cpu != -1) {

		open_counters(profile_cpu, target_pid, forks);

		open_counters(profile_cpu, pid);

	} else {

		nr_cpus = read_cpu_map();

		for (i = 0; i < nr_cpus; i++)

			open_counters(cpumap[i], target_pid, forks);

			open_counters(cpumap[i], pid);

	}



	if (file_new) {

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