LinuxConf Europe 2007

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Duxford Excursion (Monday)

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Kernel Summit 2007

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Michael Meeks - Novell, Inc

IO/grind - A new profiler

I/O latency is the dominating factor in desktop application startup performance. It is also one of the hardest things to measure in a reliable and deterministic fashion. Wall-clock timings on just-booted, quiescent systems give unfeasibly large jitter making optimizing cold-start times extremely difficult.

Measures of warm vs. cold start show eg. 80% of an OO.o cold start is pure I/O time. I/O grind is a new valgrind based tool that can record & simulate I/O patterns, allowing not only targeted optimization of applications, but deterministic comparisons of kernel I/O algorithms. Kernel optimization is often focused on more tractable CPU cycles, however the big wins are in I/O behavior - saving only one seek on cold OO.o startup, is the equivalent of a 500 cycle win on every system call emitted.

Submitted paper

Paper (PDF) and Paper (tgz) .