path: root/Documentation/trace
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authorDavid Sharp <dhsharp@google.com>2010-12-08 13:46:47 -0800
committerSteven Rostedt <rostedt@goodmis.org>2011-03-09 13:52:27 -0500
commit750912fa366312e9c5bc83eab352898a26750401 (patch)
treebb8e5cd1444a74ea283e3fa55607225e7fda4d70 /Documentation/trace
parent2a8247a2600c3e087a568fc68a6ec4eedac27ef1 (diff)
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>
Diffstat (limited to 'Documentation/trace')
1 files changed, 5 insertions, 0 deletions
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 67f1cc47325..1ebc24cf9a5 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -454,6 +454,11 @@ x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6]
latencies, as described in "Latency
trace format".
+ overwrite - This controls what happens when the trace buffer is
+ full. If "1" (default), the oldest events are
+ discarded and overwritten. If "0", then the newest
+ events are discarded.