ring-buffer: Add a 'dropped events' counter
The existing 'overrun' counter is incremented when the ring
buffer wraps around, with overflow on (the default). We wanted
a way to count requests lost from the buffer filling up with
overflow off, too. I decided to add a new counter instead
of retro-fitting the existing one because it seems like a
different statistic to count conceptually, and also because
of how the code was structured.
Link: http://lkml.kernel.org/r/1310765038-26399-1-git-send-email-slavapestov@google.com
Signed-off-by: Slava Pestov <slavapestov@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f6928ed..36c213f 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4385,6 +4385,9 @@
usec_rem = do_div(t, USEC_PER_SEC);
trace_seq_printf(s, "now ts: %5llu.%06lu\n", t, usec_rem);
+ cnt = ring_buffer_dropped_events_cpu(tr->buffer, cpu);
+ trace_seq_printf(s, "dropped events: %ld\n", cnt);
+
count = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);
kfree(s);
