On 2017/12/7 7:33, kan.li...@intel.com wrote:
From: Kan Liang <kan.li...@intel.com>
Switch to non-overwrite mode if kernel doesnot support overwrite
ringbuffer.
It's only effect when overwrite mode is supported.
No change to current behavior.
Signed-off-by: Kan Liang <kan.li...@intel.com>
---
tools/perf/builtin-top.c | 35 +++++++++++++++++++++++++++++++++++
1 file changed, 35 insertions(+)
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 5e15d27..7c462d6 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -931,6 +931,27 @@ static int perf_top_overwrite_check(struct perf_top *top)
return 0;
}
+static int perf_top_overwrite_fallback(struct perf_top *top,
+ struct perf_evsel *evsel)
+{
+ struct record_opts *opts = &top->record_opts;
+ struct perf_evlist *evlist = top->evlist;
+ struct perf_evsel *counter;
+
+ if (!opts->overwrite)
+ return 0;
+
+ /* only fall back when first event fails */
+ if (evsel != perf_evlist__first(evlist))
+ return 0;
+
+ evlist__for_each_entry(evlist, counter)
+ counter->attr.write_backward = false;
+ opts->overwrite = false;
+ ui__warning("fall back to non-overwrite mode\n");
+ return 1;
You can check perf_missing_features.write_backward here. Only do the
fallback
when we know the problem is caused by missing of write_backward.
+}
+
static int perf_top__start_counters(struct perf_top *top)
{
char msg[BUFSIZ];
@@ -954,6 +975,20 @@ static int perf_top__start_counters(struct perf_top *top)
try_again:
if (perf_evsel__open(counter, top->evlist->cpus,
top->evlist->threads) < 0) {
+
+ /*
+ * Specially handle overwrite fall back.
+ * Because perf top is the only tool which has
+ * overwrite mode by default, support
+ * both overwrite and non-overwrite mode, and
+ * require consistent mode for all events.
+ *
+ * May move it to generic code with more tools
+ * have similar attribute.
+ */
+ if (perf_top_overwrite_fallback(top, counter))
+ goto try_again;
+
It will unconditionally remove backward bit even if the problem
is caused by other missing feature.
Thank you.
