Re: Scheduler benchmarks - a follow-up
From: Rob Hussey
Date: Tue Sep 18 2007 - 00:30:34 EST
On 9/17/07, Ingo Molnar <mingo@xxxxxxx> wrote:
>
> * Ingo Molnar <mingo@xxxxxxx> wrote:
>
> > i've meanwhile tested hackbench 90 and the performance difference
> > between -ck and -cfs-devel seems to be mostly down to the more precise
> > (but slower) sched_clock() introduced in v2.6.23 and to the startup
> > penalty of freshly created tasks.
>
> Rob, another thing i just noticed in your .configs: you have
> CONFIG_PREEMPT=y enabled. Would it be possible to get a testrun with
> that disabled? That gives the best throughput and context-switch latency
> numbers. (CONFIG_PREEMPT might also have preemption artifacts - there's
> one report of it having _worse_ desktop latencies on certain hardware
> than !CONFIG_PREEMPT.)
I reverted the patch from before since it didn't seem to help. Do you
think it may have to do with my system having Hyper-Threading enabled?
I should have pointed out before that I don't really have a dual-core
system, just a P4 with Hyper-Threading (I loosely used core to refer
to processor).
Some new numbers for 2.6.23-rc6-cfs-devel (!CONFIG_PREEMPT and bound
to single processor)
lat_ctx:
15 2.73
16 2.74
17 2.81
18 2.74
19 2.74
20 2.73
21 2.60
22 2.74
23 2.72
24 2.74
25 2.74
hackbench:
80 11.578
81 11.991
82 11.914
83 12.026
84 12.226
85 12.347
86 12.552
87 12.655
88 13.011
89 12.941
90 13.237
pipe-test:
1 9.58
2 9.58
3 9.58
4 9.58
5 9.58
6 9.58
7 9.58
8 9.58
9 9.58
10 9.58
The obligatory graphs:
http://www.healthcarelinen.com/misc/benchmarks/BOUND_NOPREEMPT_lat_ctx_benchmark.png
http://www.healthcarelinen.com/misc/benchmarks/BOUND_NOPREEMPT_hackbench_benchmark.png
http://www.healthcarelinen.com/misc/benchmarks/BOUND_NOPREEMPT_pipe-test_benchmark.png
A cursory glance suggests that performance wrt lat_ctx and hackbench
has increased (lower numbers), but degraded quite a lot for pipe-test.
The numbers for pipe-test are extremely stable though, while the
numbers for hackbench are more erratic (which isn't saying much since
the original numbers gave nearly a straight line). I'm still willing
to try out any more ideas.
Regards,
Rob
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