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Subject: Re: [PATCHv11 2.6.36-rc2-tip 5/15]  5: uprobes: Uprobes
 (un)registration and exception handling.
From: Peter Zijlstra <peterz@infradead.org>
To: Christoph Hellwig <hch@infradead.org>
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Date: Mon, 06 Sep 2010 23:06:08 +0200
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On Mon, 2010-09-06 at 16:40 -0400, Christoph Hellwig wrote:

> But that is just the interface - these probes don't nessecarily have to
> be armed and cause global overhead once they are define.  If the
> implenmentation is smart enough it will defer arming the probe until
> we actually use it, and that will be per-process quite often.

The implementation I outlined a few messages ago, would in fact, as you
suggest, avoid arming things when not needed.


> The other things is that perf currently only supports per-kernel pid
> recording, while we'd really need per Posix process, which may contain
> multiple threads for useful tracing of complex userspace applications.
> I also suspect that this will fit the uprobes model much better given
> that the probes will be in any given address space.

perf does report both:

         *      { u32                   pid, tid; } && PERF_SAMPLE_TID

the pid is the process id (thread group leader like) and tid is the
task/thread id.