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>
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index aeab9c4..8786629 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -37,6 +37,7 @@
static int inherit = 1;
static int force = 0;
static int append_file = 0;
+static int verbose = 0;
static long samples;
static struct timeval last_read;
@@ -349,17 +350,35 @@
track = 0; /* only the first counter needs these */
+try_again:
fd[nr_cpu][counter] = sys_perf_counter_open(attr, pid, cpu, group_fd, 0);
if (fd[nr_cpu][counter] < 0) {
int err = errno;
- error("syscall returned with %d (%s)\n",
+ if (verbose)
+ error("sys_perf_counter_open() syscall returned with %d (%s)\n",
fd[nr_cpu][counter], strerror(err));
if (err == EPERM)
- printf("Are you root?\n");
+ die("Permission error - are you root?\n");
+
+ /*
+ * If it's cycles then fall back to hrtimer
+ * based cpu-clock-tick sw counter, which
+ * is always available even if no PMU support:
+ */
+ if (attr->type == PERF_TYPE_HARDWARE
+ && attr->config == PERF_COUNT_CPU_CYCLES) {
+
+ 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;
+ }
exit(-1);
}
+
assert(fd[nr_cpu][counter] >= 0);
fcntl(fd[nr_cpu][counter], F_SETFL, O_NONBLOCK);
@@ -519,6 +538,8 @@
"profile at this frequency"),
OPT_INTEGER('m', "mmap-pages", &mmap_pages,
"number of mmap data pages"),
+ OPT_BOOLEAN('v', "verbose", &verbose,
+ "be more verbose (show counter open errors, etc)"),
OPT_END()
};