perf record: Fall back to cpu-clock-ticks if no PMU

On architectures/CPUs without PMU support but with perfcounters
enabled 'perf record' currently fails because it cannot create a
cycle based hw-perfcounter.

Fall back to the cpu-clock-tick sw-perfcounter in this case, which
is hrtimer based and will always work (as long as perfcounters
are enabled).

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 10 insertions, 4 deletions

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 6da30a140e86..1f8c97d5c32e 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -65,6 +65,7 @@ static int			group				=  0;
 static unsigned int             page_size;
 static unsigned int             mmap_pages                      = 16;
 static int                      freq                            =  0;
+static int                      verbose                         =  0;
 
 static char                     *sym_filter;
 static unsigned long            filter_start;
@@ -550,11 +551,12 @@ try_again:
         if (fd[i][counter] < 0) {
                 int err = errno;
 
-                error("sys_perf_counter_open() syscall returned with %d (%s)\n",
-                        fd[i][counter], strerror(err));
+                if (verbose)
+                        error("sys_perf_counter_open() syscall returned with %d (%s)\n",
+                                fd[i][counter], strerror(err));
 
                 if (err == EPERM)
-                        die(" No permission - are you root?\n");
+                        die("No permission - are you root?\n");
                 /*
                  * If it's cycles then fall back to hrtimer
                  * based cpu-clock-tick sw counter, which
@@ -563,7 +565,9 @@ try_again:
                 if (attr->type == PERF_TYPE_HARDWARE
                         && attr->config == PERF_COUNT_CPU_CYCLES) {
 
-                        warning(" ... trying to fall back to cpu-clock-ticks\n");
+                        if (verbose)
+                                warning(" ... trying to fall back to cpu-clock-ticks\n");
+
                         attr->type = PERF_TYPE_SOFTWARE;
                         attr->config = PERF_COUNT_CPU_CLOCK;
                         goto try_again;
@@ -673,6 +677,8 @@ static const struct option options[] = {
                     "profile at this frequency"),
         OPT_INTEGER('E', "entries", &print_entries,
                     "display this many functions"),
+        OPT_BOOLEAN('v', "verbose", &verbose,
+                    "be more verbose (show counter open errors, etc)"),
         OPT_END()
 };