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

Ariel Weisberg ariel at weisberg.ws
Tue Feb 12 17:31:50 EST 2013


Hi,

Sorry, I am talking about active threads since there is a thread per
shard and you can choose how many you want to have. 10s of idle threads
seems to have no negative impact, and I have not experimented with more
then that.

Thanks,
Ariel

On Tue, Feb 12, 2013, at 05:04 PM, thurston at nomagicsoftware.com wrote:
>   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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> >>> Concurrency-interest at cs.oswego.edu
> >>> http://cs.oswego.edu/mailman/listinfo/concurrency-interest [2]
> >>
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> >
> >
> >
> > Links:
> > ------
> > [1] http://www.typesafe.com/
> > [2] http://cs.oswego.edu/mailman/listinfo/concurrency-interest
> 



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