On Tue, 14 Jan 2025 10:18:06 +0900
Masami Hiramatsu (Google) <[email protected]> wrote:
> > I'd rather just nuke the calltime and rettime from struct ftrace_graph_ret.
> >
>
> Yeah, this one is good to me. But this will make a slightly different time
> for the same function when we enable multiple function graph tracer on
> different instances (mine records it once and reuse it but this will record
> on each instance). We may need to notice it on the document. :)
And I believe it's separate for each instance now anyway, so I was going to
send this to Linus as well:
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index 272464bb7c60..2b74f96d09d5 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -810,6 +810,12 @@ Here is the list of current tracers that may be configured.
to draw a graph of function calls similar to C code
source.
+ Note that the function graph calculates the timings of when the
+ function starts and returns internally and for each instance. If
+ there are two instances that run function graph tracer and traces
+ the same functions, the length of the timings may be slightly off as
+ each read the timestamp separately and not at the same time.
+
"blk"
The block tracer. The tracer used by the blktrace user
>
> Reviewed-by: Masami Hiramatsu (Google) <[email protected]>
Thanks,
-- Steve
