tracing: Add an 'overwrite' trace_option.

Add an "overwrite" trace_option for ftrace to control whether the buffer should
be overwritten on overflow or not. The default remains to overwrite old events
when the buffer is full. This patch adds the option to instead discard newest
events when the buffer is full. This is useful to get a snapshot of traces just
after enabling traces. Dropping the current event is also a simpler code path.

Signed-off-by: David Sharp <dhsharp@google.com>
LKML-Reference: <1291844807-15481-1-git-send-email-dhsharp@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 856e73cc1d3f..951d0b7e7062 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -606,6 +606,7 @@ enum trace_iterator_flags {
         TRACE_ITER_SLEEP_TIME           = 0x40000,
         TRACE_ITER_GRAPH_TIME           = 0x80000,
         TRACE_ITER_RECORD_CMD           = 0x100000,
+        TRACE_ITER_OVERWRITE            = 0x200000,
 };
 
 /*