[concurrency-interest] Some interesting (confusing?) benchmark results

Aleksey Shipilev aleksey.shipilev at oracle.com
Tue Feb 12 16:24:51 EST 2013


On 02/13/2013 01:18 AM, √iktor Ҡlang wrote:
> On Tue, Feb 12, 2013 at 8:28 PM, Kirk Pepperdine <kirk at kodewerk.com
> <mailto:kirk at kodewerk.com>> wrote:
> 
>     >
>     > Do you agree that thread pool sizing depends on type of work? (IO
>     bound vs CPU bound, bursty vs steady etc etc)
>     Yes
>     > Do you agree that a JVM Thread is not a unit of parallelism?
>     Yes
>     > Do you agree that having more JVM Threads than hardware threads is
>     bad for CPU-bound workloads?
>     No, even with CPU bound workloads I have found that the hardware/OS
>     is much better at managing many workloads across many threads than I
>     am. So a few more threads is ok, many more threads is bad fast.
> 
> 
> That's an interesting observation. Have any more data on that? (really
> interested)
> As I said earlier, for CPU-bound workloads we've seen the best
> performance when only loading 60-70% of the cores (other threads exist
> on the machine of course).

I could relate to this observation if "performance" in Viktor's
statement has the significant "latency" component. "pure throughput"
things indeed have the behavior Kirk mentions.

-Aleksey.



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