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Re: ping: [v2][PATCH] Framework for performance benchmarking offunctions
On Thu, Jan 17, 2013 at 10:38:56PM +0530, Siddhesh Poyarekar wrote:
> 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.
... or maybe it's just easier using clock() or times().