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Diffstat (limited to 'Documentation/markers.txt')
| -rw-r--r-- | Documentation/markers.txt | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/Documentation/markers.txt b/Documentation/markers.txt index d2b3d0e91b2..951a2f342b9 100644 --- a/Documentation/markers.txt +++ b/Documentation/markers.txt @@ -15,10 +15,12 @@ provide at runtime. A marker can be "on" (a probe is connected to it) or "off" (no probe is attached). When a marker is "off" it has no effect, except for adding a tiny time penalty (checking a condition for a branch) and space penalty (adding a few bytes for the function call at the end of the -instrumented function and adds a data structure in a separate section). When a -marker is "on", the function you provide is called each time the marker is -executed, in the execution context of the caller. When the function provided -ends its execution, it returns to the caller (continuing from the marker site). +instrumented function and adds a data structure in a separate section). The +immediate values are used to minimize the impact on data cache, encoding the +condition in the instruction stream. When a marker is "on", the function you +provide is called each time the marker is executed, in the execution context of +the caller. When the function provided ends its execution, it returns to the +caller (continuing from the marker site). You can put markers at important locations in the code. Markers are lightweight hooks that can pass an arbitrary number of parameters, @@ -90,6 +92,13 @@ notrace void probe_tracepoint_name(unsigned int arg1, struct task_struct *tsk) /* write data to trace buffers ... */ } +* Optimization for a given architecture + +To force use of a non-optimized version of the markers, _trace_mark() should be +used. It takes the same parameters as the normal markers, but it does not use +the immediate values based on code patching. + + * Probe / marker example See the example provided in samples/markers/src |