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Re: ping: [v2][PATCH] Framework for performance benchmarking offunctions
On Thu, Jan 17, 2013 at 10:46:25AM -0600, Steven Munroe wrote:
> On many platforms clock_gettime() still requires a system call, which is
> swamp the measurement you are trying to make.
> You need to make sure there are enough iterations within the BENCH_FUCC
> so that the clock_gettime(0 overhead is less then 1% of the total.
Oh yes, and that will make it difficult to measure fast paths in math
functions (but do we need to measure them at all to begin with?). The
slow paths are currently slow enough that it's easy to have them
running up to 30 seconds or so on a few million iterations. That
should cover the syscalls just fine.