[zeromq-dev] Java NIO selector minimum possible latency

[Julie Anderson]

Hi Michel,

Question was about the latency to wake up a quiet thread blocking on a
select. The answer was already given to me: busy spinning. I was able to
pull down the latency to around 60 micros for a a single packet. As you
increase the number of packets it goes down exponentially to 10 micros. I
even get some packets doing the round trip in 8 micros.

Does ZeroMQ support some kind of reliable UDP for a publisher-subscriber /
one-to-many asynchronous messaging system?

-J

On Sat, Aug 25, 2012 at 12:24 PM, Michel Pelletier <
pelletier.michel at gmail.com> wrote:

> On Thu, Aug 23, 2012 at 1:12 PM, Julie Anderson
> <julie.anderson.uk at gmail.com> wrote:
> >
> > Hi,
> >
>
> <Java NIO UDP benchmark results snipped>
>
> > So my questions for the community are:
> >
> > 1 - Is my minimum time of 13 micros with average of 19 micros optimum for
> > this round trip packet test. It looks like I am beating ZeroMQ by far so
> I
> > may be missing something here. From this benchmark it looks like ZeroMQ
> has
> > a 49 micros avg time (99% percentile) on a standard kernel =>
> > http://www.zeromq.org/results:rt-tests-v031
>
> It seems to me that you are comparing two very different things here.
> The time to send a udp packet back and forth in a tight single
> threaded selector loop is definitely going to be faster than a message
> being sent back and forth using tcp as 0mq does, and then add on top
> the overhead of 0mq managing the message across a thread boundary from
> your application code to the core library.  The udp approach is going
> to be faster, by far.  Of course it doesn't seem likely your NIO code
> offers the same feature set as the 0mq library does from a messaging
> framework point of view.
>
> > 2 - Is there anything I can do to improve the selector reaction time
> when I
> > spin a single or very few messages? 150 micros does not look good. Or
> should
> > I assume that on a prod environment the selector will never be quite?
>
> So is this a Java NIO question?  Or are you asking how our 49ms beats
> your 150?  I think you meant "quiet" instead of "quite", but I'm still
> confused as to the question.  Maybe post your benchmark code and we
> can get some insight into what you're asking.
>
> -Michel
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