Ingo Molnar wrote:
> * Alexander van Heukelum <[EMAIL PROTECTED]> wrote:
>
> hackbench is _way_ too noisy to measure such cycle-level differences
> as irq entry changes cause. It also does not really stress interrupts
> - it only stresses networking, the VFS and the scheduler.
>
> a better test might have been to generate a ton of interrupts, but
> even then it's _very_ hard to measure it properly. The best method is
> what i've suggested to you early on: run a loop in user-space and
> observe irq costs via RDTSC, as they happen. Then build a histogram
> and compare the before/after histogram. Compare best-case results as
> well (the first slot of the histogram), as those are statistically
> much more significant than a noisy average.
>
For what it's worth, I tested this out, and I'm pretty sure you need to
run a uniprocessor configuration (or system) for it to make sense --
otherwise you end up missing too many of the interrupts. I first tested
this on an 8-processor system and, well, came up with nothing.
I'm going to try this later on a uniprocessor, unless Alexander beats me
to it.
-hpa
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