* Rob Hussey <robjhussey@gmail.com> wrote:

quoted text
> 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

btw., it's likely that if you turn off CONFIG_PREEMPT for .21 and for 
.22-ck1 they'll improve a bit too - so it's not fair to put the .23 
!PREEMPT numbers on the graph as the PREEMPT numbers of the other 
kernels. (it shows the .23 scheduler being faster than it really is)

quoted text
> 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.

the pipe-test behavior looks like an outlier. !PREEMPT only removes code 
(which makes the code faster), so this could be a cache layout artifact. 
(or perhaps we preempt at a different point which is disadvantageous to 
caching?) Pipe-test is equivalent to "lat_ctx -s 0 2" so if there was a 
genuine slowdown it would show up in the lat_ctx graph - but the graph 
shows a speedup.

	Ingo
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