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authorTom Zanussi <tom.zanussi@linux.intel.com>2018-01-16 05:51:41 +0300
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2018-03-11 00:05:51 +0300
commit2c1ea60b195da6c4661ec5e4d61f68b8b34e113b (patch)
tree73c462753b91be9301b6e7ddcef1439e53285e22 /Documentation/trace
parentdc4e2801d400b0346fb281ce9cf010d611e2243c (diff)
downloadlinux-2c1ea60b195da6c4661ec5e4d61f68b8b34e113b.tar.xz
tracing: Add timestamp_mode trace file
Add a new option flag indicating whether or not the ring buffer is in 'absolute timestamp' mode. Currently this is only set/unset by hist triggers that make use of a common_timestamp. As such, there's no reason to make this writeable for users - its purpose is only to allow users to determine unequivocally whether or not the ring buffer is in that mode (although absolute timestamps can coexist with the normal delta timestamps, when the ring buffer is in absolute mode, timestamps written while absolute mode is in effect take up more space in the buffer, and are not as efficient). Link: http://lkml.kernel.org/r/e8aa7b1cde1cf15014e66545d06ac6ef2ebba456.1516069914.git.tom.zanussi@linux.intel.com Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'Documentation/trace')
-rw-r--r--Documentation/trace/ftrace.txt24
1 files changed, 24 insertions, 0 deletions
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index d4601df6e72e..54213e5c23f6 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -539,6 +539,30 @@ of ftrace. Here is a list of some of the key files:
See events.txt for more information.
+ timestamp_mode:
+
+ Certain tracers may change the timestamp mode used when
+ logging trace events into the event buffer. Events with
+ different modes can coexist within a buffer but the mode in
+ effect when an event is logged determines which timestamp mode
+ is used for that event. The default timestamp mode is
+ 'delta'.
+
+ Usual timestamp modes for tracing:
+
+ # cat timestamp_mode
+ [delta] absolute
+
+ The timestamp mode with the square brackets around it is the
+ one in effect.
+
+ delta: Default timestamp mode - timestamp is a delta against
+ a per-buffer timestamp.
+
+ absolute: The timestamp is a full timestamp, not a delta
+ against some other value. As such it takes up more
+ space and is less efficient.
+
hwlat_detector:
Directory for the Hardware Latency Detector.