On Sat, 21 Jan 2023, John Ference wrote:
*NB. Questions: What's the underlying behavior? Is this intended?*
I can't reproduce this. I get:
,.10{.res
0.117785
0.113945
0.116619
0.0783475
0.114737
0.0741682
0.0747921
0.0674546
0.0765281
0.0777421
,._10{.res
0.0718152
0.0694659
0.0721551
0.0667192
0.0680241
0.070355
0.0709015
0.0657318
0.064728
0.066456
That the first few timings are slower is to be expected, as the CPU is warming
up. But there doesn't seem to be any periodic bias such as you see.
One idea (and I am just spitballing here): you have an amd cpu (I am assuming,
given that you have 6 threads), and amd cpus have numa cache, which might
somehow bias the work distribution. Whereas I have an intel cpu, and those
have uma cache. (Or, if it's a newer intel cpu, could be big.little screwing
things up.)
NB. Why wouldn't each pool use its own threads for multi-threaded
primitives?
Different workloads can be bottlenecked by different things. If you are
bottlenecked by i/o, you might want to have more threads than cores. But if
you are bottlenecked by compute or memory, having more threads than cores just
adds overhead. So you might have, e.g., threadpool 1 for i/o and threadpool 0
for compute, with appropriate numbers of threads in each.
Something I want to do (but haven't implemented yet) is to let each pool pick
which threadpool it punts its work to. So e.g. you could have 4 threadpools:
i/o for numa node 0, compute for numa node 0, i/o for numa node 1, compute for
numa node 1.
NB. What's the point of creating a second pool with multiple threads, rather
than separate pools?
What do you mean by this?
NB. How is resource contention between pools adjudicated?
Which resources?
-E
P.S. very sorry for not responding yet to your earlier email--I have been tied
up, but haven't forgotten it!
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