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Subject[PATCH 1/3] perf stat: Enable counters when collecting process-wide or system-wide data
Date
From: Zhang, Yanmin <yanmin_zhang@linux.intel.com>

Command 'perf stat' doesn't enable counters when collecting an existing
(by -p) process or a system-wide statistics. Fix the issue.

Change the condition of fork/exec subcommand. If there is a subcommand
parameter, perf always fork/exec it. The usage example is:

# perf stat -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 use CTRL+C to stop it without precise time clock.

Another issue is 'perf stat -a' consumes 100% time of a full single
logical cpu. It has a bad impact on running workload. Fix it by adding a
sleep(1) in the while(!done) loop in function run_perf_stat.
Signed-off-by: Zhang Yanmin <yanmin_zhang@linux.intel.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sheng Yang <sheng@linux.intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Jes Sorensen <Jes.Sorensen@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Zachary Amsden <zamsden@redhat.com>
Cc: <zhiteng.huang@intel.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-stat.c | 24 ++++++++++++++----------
1 files changed, 14 insertions(+), 10 deletions(-)
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 95db31c..5f41244 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -159,8 +159,10 @@ static void create_perf_stat_counter(int counter, int pid)
}
} else {
attr->inherit = inherit;
- attr->disabled = 1;
- attr->enable_on_exec = 1;
+ if (target_pid == -1) {
+ attr->disabled = 1;
+ attr->enable_on_exec = 1;
+ }

fd[0][counter] = sys_perf_event_open(attr, pid, -1, -1, 0);
if (fd[0][counter] < 0 && verbose)
@@ -251,9 +253,9 @@ static int run_perf_stat(int argc __used, const char **argv)
unsigned long long t0, t1;
int status = 0;
int counter;
- int pid = target_pid;
+ int pid;
int child_ready_pipe[2], go_pipe[2];
- const bool forks = (target_pid == -1 && argc > 0);
+ const bool forks = (argc > 0);
char buf;

if (!system_wide)
@@ -265,10 +267,10 @@ static int run_perf_stat(int argc __used, const char **argv)
}

if (forks) {
- if ((pid = fork()) < 0)
+ if ((child_pid = fork()) < 0)
perror("failed to fork");

- if (!pid) {
+ if (!child_pid) {
close(child_ready_pipe[0]);
close(go_pipe[1]);
fcntl(go_pipe[0], F_SETFD, FD_CLOEXEC);
@@ -297,8 +299,6 @@ static int run_perf_stat(int argc __used, const char **argv)
exit(-1);
}

- child_pid = pid;
-
/*
* Wait for the child to be ready to exec.
*/
@@ -309,6 +309,10 @@ static int run_perf_stat(int argc __used, const char **argv)
close(child_ready_pipe[0]);
}

+ if (target_pid == -1)
+ pid = child_pid;
+ else
+ pid = target_pid;
for (counter = 0; counter < nr_counters; counter++)
create_perf_stat_counter(counter, pid);

@@ -321,7 +325,7 @@ static int run_perf_stat(int argc __used, const char **argv)
close(go_pipe[1]);
wait(&status);
} else {
- while(!done);
+ while(!done) sleep(1);
}

t1 = rdclock();
@@ -459,7 +463,7 @@ static volatile int signr = -1;

static void skip_signal(int signo)
{
- if(target_pid != -1)
+ if(child_pid == -1)
done = 1;

signr = signo;
--
1.6.2.5


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