[concurrency-interest] Benchmark to demonstrate improvement in thread management over the years.

Kimo Crossman kimo at webnetic.net
Tue Aug 13 06:33:29 EDT 2013


I thought current Linux scheduler CFS was O(1)

http://en.wikipedia.org/wiki/O(1)_scheduler


On Tue, Aug 13, 2013 at 1:49 AM, Kirk Pepperdine <kirk at kodewerk.com> wrote:

>
> On 2013-08-13, at 8:38 AM, James Roper <james.roper at typesafe.com> wrote:
>
> On Tue, Aug 13, 2013 at 2:59 PM, Unmesh Joshi <unmeshjoshi at gmail.com>wrote:
>
>> Hi James,
>>
>> At what number of threads JVM or OS performance starts degrading? Or
>> number of threads start becoming the main bottleneck in the system?
>>
>
> Really, you just need to do your own load testing specific to your own
> application, hardware and OS requirements.  The current Linux scheduler
> runs in O(log N),
>
>
> Really? I thought it was using an O(N) heap sort. Anyways, IME, the bigger
> problem is that getting the thread scheduler scheduled so that you can get
> threads scheduled... (there might be a Dr. Seuss thing going on here).
>
>
>
> so technically, that means performance starts degrading at 2 threads,
> since every thread added increases the amount of time the scheduler takes.
>  But of course, that degradation is negligible compared to the amount of
> time your app spends waiting for IO.  So it all depends on your app, what
> it's doing, and what its requirements are.
>
> It's not just scheduling that gets impacted, another obvious one that I
> already I pointed out was memory consumption, so once the thread stacks
> have consumed all available RAM, then they won't just be the bottleneck,
> your application will slow to a crawl or even crash.
>
>
> Slow is something due to something else. No more stack space leads to OOME
> Stack space exhausted. Is this what you mean?
>
> Regards,
> Kirk
>
>
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