Messages in this thread | | | Date | Wed, 14 Dec 2011 17:34:09 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 2/2] trace,x86: Add x86 irq vector entry/exit tracepoints |
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On Wed, Dec 14, 2011 at 10:09:11AM -0500, Seiji Aguchi wrote: > Thank you for giving me a comment. > Unfortunately, neither "perf record" nor "ftrace" works for me. > > >What about using perf for that? > > > >Just run: > > > > perf record -ag > > ^C > > perf report > > > >And you should find in the callchains some informations about where your CPUs > >are spending time. > > > >If you system is too slow for that > > When system is too slow, user command such as "perf record" may not work. > > >but you're doing background tracing with > >ftrace, you can use stacktrace with ftrace. > > Actually, We're doing background tracing in our customer's system rather than kernel debugging. > Ftrace doesn't work for me because it checks the size of the stack at every function call. > Our customers are seriously concerned about its overhead. > > For reducing the overhead, I need tracepoints so we can hook minimal function calls.
Well ftrace is a whole subsystem that includes the function tracer and also an interface for tracepoints in debugfs. I was rather suggesting the latter one. This is a good choice for background tracing. And it supports stacktraces. If those generate too much overhead perhaps you can tune the number of entries in the stacktrace, I don't remember if we can do that currently but this can be an interesting feature.
What are you using currently for the background tracing?
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