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Date: Wed, 26 Sep 2007 22:07:50 +0530 From: "Abhishek Sagar" <sagar.abhishek@...il.com> To: "Avishay Traeger" <atraeger@...sunysb.edu> Cc: prasanna@...ibm.com, ananth@...ibm.com, anil.s.keshavamurthy@...el.com, davem@...emloft.net, linux-kernel@...r.kernel.org Subject: Re: KPROBES: Instrumenting a function's call site On 9/26/07, Avishay Traeger <atraeger@...sunysb.edu> wrote: > So to measure the latency of foo(), I basically want kprobes to do this: > pre_handler(); > foo(); > post_handler(); > > The problem is that the latencies that I am getting are consistently low > (~10,000 cycles). When I manually instrument the functions, the latency > is about 20,000,000 cycles. Clearly something is not right here. Single-stepping is done with preemption (and on some archs like ARM, interrupts) disabled. May be that is contributing to such a skew. > Is this a known issue? Instead of using the post-handler, I can try to > add a kprobe to the following instruction with a pre-handler. I was > just curious if there was something fundamentally wrong with the > approach I took, or maybe a bug that you should be made aware of. > > Please CC me on any replies (not subscribed to LKML). > > Thanks, > Avishay > -- Regards Abhishek Sagar - > 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/ - 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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