Re: [PATCH] CFS: Fix missing digit off in wmult table

From: Matt Mackall
Date: Mon Jul 16 2007 - 16:32:52 EST


On Mon, Jul 16, 2007 at 04:01:17PM +0200, Roman Zippel wrote:
> Hi,
>
> On Mon, 16 Jul 2007, Ingo Molnar wrote:
>
> > to sum it up: a nice +19 task (the most commonly used nice level in
> > practice) gets 9.1%, 3.9%, 3.1% of CPU time on the old scheduler,
> > depending on the value of HZ. This is quite inconsistent and illogical.
>
> You're correct that you can find artifacts in the extreme cases, it's
> subjective whether this is a serious problem.
> It's nice that these artifacts are gone, but that still doesn't explain
> why this ratio had to be increase that much from around 1:10 to 1:69.

More dynamic range is better? If you actually want a task to get 20x
the CPU time of another, the older scheduler doesn't really allow it.

Getting 1/69th of a modern CPU is still a fair number of cycles.
Nevermind 1/69th of a machine with > 64 cores.

--
Mathematics is the supreme nostalgia of our time.
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