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

Con Kolivas
2004-06-08T05:26:00Z

Quoting Andrew Morton <akpm@osdl.org>:

> 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.

Ordinary kernbench on 8x OSDL hardware fails to show anything like this:
Summary:
time in seconds for optimal run:
2.6.7-rc2: 129.948
2.6.7-rc2-s6.3: 129.528
2.6.7-rc2-s6.3compute: 127.63

Detailed:
kernel: patch-2.6.7-rc2
plmid: 2987
Host: stp8-002
Average Optimal -j 32 Load Run:
Elapsed Time 129.948
User Time 873.302
System Time 86.318
Percent CPU 738
Context Switches 39853.4
Sleeps 29045.8
Average Maximal -j Load Run:
Elapsed Time 128.362
User Time 866.274
System Time 84.352
Percent CPU 740
Context Switches 25742.6
Sleeps 20615.8
Average Half Load -j 4 Run:
Elapsed Time 231.04
User Time 833.69
System Time 72.94
Percent CPU 392
Context Switches 12672.2
Sleeps 22267.2

kernel: staircase6.2
plmid: 3002
Host: stp8-002
Average Optimal -j 32 Load Run:
Elapsed Time 129.528
User Time 873.866
System Time 85.372
Percent CPU 740.2
Context Switches 38286.6
Sleeps 28331
Average Maximal -j Load Run:
Elapsed Time 128.074
User Time 862.728
System Time 85.842
Percent CPU 740.2
Context Switches 20894
Sleeps 22189.2
Average Half Load -j 4 Run:
Elapsed Time 230.942
User Time 833.03
System Time 71.126
Percent CPU 391
Context Switches 3467
Sleeps 22389.2

kernel: crunchah6.3
plmid: 3008
Host: stp8-002
Average Optimal -j 32 Load Run:
Elapsed Time 127.63
User Time 861.668
System Time 83.078
Percent CPU 739.6
Context Switches 19818.4
Sleeps 28442.6
Average Maximal -j Load Run:
Elapsed Time 127.354
User Time 856.632
System Time 82.952
Percent CPU 737
Context Switches 12389.2
Sleeps 21788.6
Average Half Load -j 4 Run:
Elapsed Time 230.8
User Time 833.378
System Time 71.304
Percent CPU 391.6
Context Switches 3738.4
Sleeps 22288.6

Con