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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: Zhang Yanmin <yanmin_zhang@linux.intel.com>
Signed-off-by: Arnaldo 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: Ingo Molnar <mingo@elte.hu>
hifive-unleashed-5.1
Zhang, Yanmin 2010-03-18 11:36:04 -03:00 committed by Ingo Molnar
parent 6be2850eff
commit 46be604b5b
1 changed files with 15 additions and 18 deletions
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33
tools/perf/builtin-record.c
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@ -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;
attr->disabled = 1;
if (forks)
if (target_pid == -1 && !system_wide) {
attr->disabled = 1;
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) {