perf record: Fix fallback to cpu-clock on ppc

perf-record on PPC is not falling back to cpu-clock:

$ perf record -ag -fo /tmp/perf.data -- sleep 1

  Error: sys_perf_event_open() syscall returned with 6 (No such device or address).  /bin/dmesg may provide additional information.

  Fatal: No CONFIG_PERF_EVENTS=y kernel support configured?

The problem is that until 2.6.37 (behavior changed with commit b0a873e)
perf on PPC returns ENXIO when hw_perf_event_init() fails. With this
patch we get the expected behavior:

$ perf record -ag -fo /tmp/perf.data -v -- sleep 1
Old kernel, cannot exclude guest or host samples.
The cycles event is not supported, trying to fall back to cpu-clock-ticks
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.151 MB /tmp/perf.data (~6592 samples) ]

Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1336490937-57106-1-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 42e2414..1a9098c 100644 (file)
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -242,9 +242,13 @@ try_again:
                        /*
                         * If it's cycles then fall back to hrtimer
                         * based cpu-clock-tick sw counter, which
-                        * is always available even if no PMU support:
+                        * is always available even if no PMU support.
+                        *
+                        * PPC returns ENXIO until 2.6.37 (behavior changed
+                        * with commit b0a873e).
                         */
-                       if (err == ENOENT && attr->type == PERF_TYPE_HARDWARE
+                       if ((err == ENOENT || err == ENXIO)
+                                       && attr->type == PERF_TYPE_HARDWARE
                                        && attr->config == PERF_COUNT_HW_CPU_CYCLES) {
 
                                if (verbose)