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Message-ID: <d092c2300701071025i16f11c50p3908c1d8427ab3b4@mail.gmail.com> Date: Sun, 7 Jan 2007 13:25:38 -0500 From: "Johnicholas Hines" <johnicholas.hines@...il.com> To: linux-kernel@...r.kernel.org Cc: ltt-dev@...tserv.shafik.org Subject: a lttng success story Hi. I was really pleased to find an intermittent timing problem using lttng, and maybe an example of how it can be used would be helpful to people considering adopting it. The system is a veterinary testing machine running Linux on an ARM board (specifically the applied data systems sphere). The symptom was that, under a certain workload, intermittently, a timing constraint was being violated. Setting the processes to debug mode (spitting out lots of messages) was too slow - many timing constraints were violated, and the workload was unrunnable. I ran the bug-revealing workload under lttng for 4 hours, and captured one abnormal event (and thousands of normal events). I waded through the lttng logs, and found that the reason for the pause was that the target of a message had, in the abnormal case, not blocked on that fd. Lttng reveals things about the state of the scheduler that are very helpful in debugging multi-process, userspace, systems. It is faster and reveals more information than anything special-purpose I could have built. To repeat myself, maybe an example of how it can be used would be helpful to people considering adopting it. Thanks for your attention, Johnicholas - 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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