perf stat: Better report failure to collect system wide stats
Before:
[acme@doppio linux-2.6-tip]$ perf stat -a sleep 1s
Performance counter stats for 'sleep 1s':
<not counted> task-clock-msecs
<not counted> context-switches
<not counted> CPU-migrations
<not counted> page-faults
<not counted> cycles
<not counted> instructions
<not counted> branches
<not counted> branch-misses
<not counted> cache-references
<not counted> cache-misses
1.016998463 seconds time elapsed
[acme@doppio linux-2.6-tip]$
Now:
[acme@doppio linux-2.6-tip]$ perf stat -a sleep 1s
No permission to collect system-wide stats.
Consider tweaking /proc/sys/kernel/perf_event_paranoid.
[acme@doppio linux-2.6-tip]$
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1269274229-20442-4-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index c92f90f..1036ca7 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -144,10 +144,11 @@
#define ERR_PERF_OPEN \
"Error: counter %d, sys_perf_event_open() syscall returned with %d (%s)\n"
-static void create_perf_stat_counter(int counter)
+static int create_perf_stat_counter(int counter)
{
struct perf_event_attr *attr = attrs + counter;
int thread;
+ int ncreated = 0;
if (scale)
attr->read_format = PERF_FORMAT_TOTAL_TIME_ENABLED |
@@ -159,9 +160,11 @@
for (cpu = 0; cpu < nr_cpus; cpu++) {
fd[cpu][counter][0] = sys_perf_event_open(attr,
-1, cpumap[cpu], -1, 0);
- if (fd[cpu][counter][0] < 0 && verbose)
- fprintf(stderr, ERR_PERF_OPEN, counter,
- fd[cpu][counter][0], strerror(errno));
+ if (fd[cpu][counter][0] < 0)
+ pr_debug(ERR_PERF_OPEN, counter,
+ fd[cpu][counter][0], strerror(errno));
+ else
+ ++ncreated;
}
} else {
attr->inherit = inherit;
@@ -172,12 +175,16 @@
for (thread = 0; thread < thread_num; thread++) {
fd[0][counter][thread] = sys_perf_event_open(attr,
all_tids[thread], -1, -1, 0);
- if (fd[0][counter][thread] < 0 && verbose)
- fprintf(stderr, ERR_PERF_OPEN, counter,
- fd[0][counter][thread],
- strerror(errno));
+ if (fd[0][counter][thread] < 0)
+ pr_debug(ERR_PERF_OPEN, counter,
+ fd[0][counter][thread],
+ strerror(errno));
+ else
+ ++ncreated;
}
}
+
+ return ncreated;
}
/*
@@ -264,7 +271,7 @@
{
unsigned long long t0, t1;
int status = 0;
- int counter;
+ int counter, ncreated = 0;
int child_ready_pipe[2], go_pipe[2];
const bool forks = (argc > 0);
char buf;
@@ -324,7 +331,16 @@
}
for (counter = 0; counter < nr_counters; counter++)
- create_perf_stat_counter(counter);
+ ncreated += create_perf_stat_counter(counter);
+
+ if (ncreated == 0) {
+ pr_err("No permission to collect %sstats.\n"
+ "Consider tweaking /proc/sys/kernel/perf_event_paranoid.\n",
+ system_wide ? "system-wide " : "");
+ if (child_pid != -1)
+ kill(child_pid, SIGTERM);
+ return -1;
+ }
/*
* Enable counters and exec the command:
@@ -587,7 +603,8 @@
status = run_perf_stat(argc, argv);
}
- print_stat(argc, argv);
+ if (status != -1)
+ print_stat(argc, argv);
return status;
}