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KernelTrap.org: KernelNewbies & OProfile: John Levon Interview

Nov 04, 2001, 20:34 (3 Talkback[s])

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Jeremy Andrews writes:

This week we spoke with John Levon, the author of OProfile and a contributer to KernelNewbies. He offers much insight into both of these projects, as well as reflecting on Linux in general. OProfile is a statistical x86 profiling system for the 2.4 Linux kernel. KernelNewbies is an excellent resource for people looking to understand the Linux kernel, comprised of a web page, an IRC channel, and a mailing list.

"JA: Who is currently using oprofile?
John Levon: SuSE are using oprofile internally for a variety of user-space and kernel tasks, including work on the networking stack. HP are using it as part of their internal tools, and have contributed to and sponsored oprofile development (they leant me an SMP machine)

JA: What exactly does it mean, to 'profile the entire system'?
John Levon: Intel and AMD provide performance counter registers on their CPUs which can count interesting events such as cache line fills. oprofile uses these counters to determine which routines in the system affect them most. Due to its design, this includes all code on the system: interrupt handlers, kernel modules, the kernel, libraries and binaries.

Other profilers focus on particular parts of the system such as a single binary. This runs the risk of mis-directing the optimisation effort. Its non-intrusive design allows oprofile to be run on production systems easily; getting more accurate data than would otherwise be possible."

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