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Message-ID: <20110207212220.GA30070@feather> Date: Mon, 7 Feb 2011 13:22:22 -0800 From: Josh Triplett <josh@...htriplett.org> To: Steven Rostedt <rostedt@...dmis.org> Cc: linux-kernel@...r.kernel.org Subject: Re: [RFC 0/4] tracing,x86_64 - function/graph trace without mcount/-pg/framepointer On Fri, Jun 23, 2000 at 10:56:55AM +0000, Steven Rostedt wrote: > On Thu, 2011-02-03 at 16:42 +0100, Jiri Olsa wrote: > > hi, > > > > I recently saw the direct jump probing made for kprobes > > and tried to use it inside the trace framework. > > > > The global idea is patching the function entry with direct > > jump to the trace code, instead of using pregenerated gcc > > profile code. > > Interesting, but ideally, it would be nice if gcc provided a better > "mcount" mechanism. One that calls mcount (or whatever new name it would > have) before it does anything with the stack. GCC 4.6 may help here. According to http://gcc.gnu.org/gcc-4.6/changes.html: "Support for emitting profiler counter calls before function prologues. This is enabled via a new command-line option -mfentry." Looks like that option might only support x86 (32-bit and 64-bit) at the moment, but it still seems like an improvement over the current mechanism to work around GCC's placement of mcount. - Josh Triplett -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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