dtrace users opinion solicited (timestamps)
Robert Watson
rwatson at FreeBSD.org
Fri Jul 10 11:12:39 UTC 2009
On Fri, 10 Jul 2009, Andriy Gapon wrote:
> Thinking aloud - maybe we could always use one value of tsc_freq (or
> something like max_tsc_freq). This wouldn't give us correct timestamps when
> TSC frequency is changing, but it would give us something that is always
> proportional to TSC value and thus has its properties - monotonicity in the
> first place. And, of course, there is no problem when TSC frequency is
> constant.
Just a point from a user perspective: I find it useful (important even) to be
able to compare timing between runs on the same box, and while that means I
need to control for the frequency changing in an experimental sense, in as
much as timestamp measurements in dtrace can be normalized, that would be
helpful.
Robert N M Watson
Computer Laboratory
University of Cambridge
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