Re: [PATCH] Staircase Scheduler v6.3 for 2.6.7-rc2

Andrew Morton
2004-06-08T02:51:02Z

Phy Prabab <phyprabab@yahoo.com> wrote:
>
> Also please note the degredation between
> 2.6.7-rc2-bk8-s63:
>
> A: 35.57user 38.18system 1:20.28elapsed 91%CPU
> B: 35.54user 38.40system 1:19.48elapsed 93%CPU
> C: 35.48user 38.28system 1:20.94elapsed 91%CPU
>
> Interesting how much more time is spent in both user
> and kernel space between the two kernels. Also note
> that 2.4.x exhibits even greater delta:
>
> A: 28.32user 29.51system 1:01.17elapsed 93%CPU
> B: 28.54user 29.40system 1:01.48elapsed 92%CPU
> B: 28.23user 28.80system 1:00.21elapsed 94%CPU
>
> Could anyone suggest a way to understand why the
> difference between the 2.6 kernels and the 2.4
> kernels?

This is very very bad.

It's a uniprocessor machine, yes?

Could you describe the workload a bit more? Is it something which others
can get their hands on?

It spends a lot of time in the kernel for a build system. I wonder why.

At a guess I'd say either a) you're hitting some path in the kernel which
is going for a giant and bogus romp through memory, trashing CPU caches or
b) your workload really dislikes run-child-first-after-fork or c) the page
allocator is serving up pages which your access pattern dislikes or d)
something else.

It's certainly interesting.