I too had the same intuition that DTrace works completely in software,
but after knowing that there is Performance Monitoring Unit(PMU)
present in intel's chip, so I got confused if DTRace uses it, also
same type of hardware is present in AMD's chip. I might be wrong.
The intel/amd microprocessors provide acess to performance counters
which can be programmed to gather information about
hardware events like number of instructions executed, number of cache
misses ...
The 'cpc' provider in DTrace makes available probes which are
associated to these performance counters.
More details at:
http://wikis.sun.com/display/DTrace/cpc+Provider
I'm sure Pramod was just citing Intel/AMD as that was in the
original question but just to be clear; the cpc provider gives
access to the performance counters on any platform that Solaris
runs on**.
Jon.
** Apart from the old USI/II processors as the performance counter
back-end doesn't provide a counter overflow mechanism. However, if
you're doing performance analysis on one of these processors, you've
got *way* bigger problems than that...
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