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

thurston at nomagicsoftware.com thurston at nomagicsoftware.com
Tue Feb 12 17:04:01 EST 2013


  Even when those additional threads are idle?

> I have noticed the execution time of
> transactions increases as you add threads even though there is no
> state shared between threads/transactions and there are fewer threads
> then cores.
>
>  Thanks,
>  Ariel
>
>  On Tue, Feb 12, 2013, at 04:24 PM, Vitaly Davidovich wrote:
>
>> For pure CPU bound work, I typically add 1 or maybe 2 more threads 
>> than # of hardware threads; this is to account for hardware threads 
>> possibly hitting a hard page fault and getting suspended. I don't see 
>> how having any more than that threads benefits perf.
>>
>> Sent from my phone
>> On Feb 12, 2013 4:21 PM, "√iktor Ҡlang" <viktor.klang at gmail.com> 
>> wrote:
>>
>>> On Tue, Feb 12, 2013 at 8:28 PM, Kirk Pepperdine 
>>> <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).
>>>
>>> Cheers,
>>>
>>>>>>
>>>> Regards,
>>>> Kirk
>>>
>>> --
>>>
>>> Viktor Klang
>>> Director of Engineering
>>>
>>> Typesafe [1] - The software stack for applications that scale
>>> Twitter: @viktorklang
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>>
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>
>
> Links:
> ------
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