Messages in this thread | | | Subject | Re: [RFC][PATCH 0/4] ftrace: Use -mfentry when supported (this is for x86_64 right now) | From | Steven Rostedt <> | Date | Fri, 18 Feb 2011 10:07:39 -0500 |
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On Fri, 2011-02-18 at 20:45 +0900, Masami Hiramatsu wrote: > (2011/02/18 5:11), Steven Rostedt wrote: > > On Fri, 2011-02-18 at 01:07 +0900, Masami Hiramatsu wrote: > > > >> I just thought that frequent stop-machine is not so good from the user's > >> POV. I agree that disabled probe ignoring the call is enough. > >> Maybe, it could be done with the similar mechanism of jump optimization. > > > > I thought jump optimization still calls stop_machine too? > > Yes, but now it does batch optimization. > Even if hundreds kprobes are registered separately, jump optimization > has been done in background with a stop_machine per every 256 probes. > (Until optimizing, kprobes can use breakpoints instead)
But a single optimized kprobe still must use stopmachine.
But it is true that the function tracer does it as one big shot. That is, it will do all functions in a single stop machine that needs to be changed. It too is batched, but there is not a limit to that batch.
I would be interested in hearing from users and real use cases that someone would like to trace functions but stopmachine is too big of a hammer.
-- Steve
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