Re: [RFC patch] CFS fix place entity spread issue (v2)

[Linus Torvalds <torvalds@linux-foundation.org>]

On Sun, 18 Apr 2010, Mathieu Desnoyers wrote:
>
> CFS fix place entity spread issue (v2)
> 
> Huge CFS vruntime spread (18 minutes) has been observed with LTTng while simply
> running Xorg on a uniprocessor machine. Detailed explanation in my ELC2010
> presentation at:

Hmm. I tested this patch with my favourite non-scientific desktop load 
test: do web browsing while doing a kernel compile with "make -j16" (after 
doing a "git clean -dqfx" and "ccache -C" to get rid of old object files 
and ccache).

This is on a dual-core (with SMT, so 4 threads) Core i5, so "make -j16" 
overcommits the CPU's quite a bit.

And quite frankly, I think your patch makes things much worse. I don't 
have numbers, but it felt much choppier and slower to do scrolling in 
firefox o moving windows around while the load average is 20+.

My testload is in no way objective, nor necessarily any good, but it's the 
one I happen to use, and while it's subjective, I think the difference was 
pretty clear and not good.

			Linus