Re: [Discuss-gnuradio] Latency measurements with Unix-domain sockets

[Alexander Chemeris]

On Tue, May 31, 2011 at 15:24, Andre Puschmann
<address@hidden> wrote:
> On 05/31/2011 10:54 AM, Alexander Chemeris wrote:
>> On Tue, May 31, 2011 at 03:07, Marcus D. Leech <address@hidden> wrote:
>>> I used the following two little programs:
>>> <skip>
>>>
>>> And found no significant difference in peak and average latencies
>>> between them.
>>>
>>> The unixdomain_server takes a single command-line argument which tells
>>> it how many samples
>>>  to average over before producing a printed result.
>>>
>>> So this confirms my earlier assertion that I would be surprised to find
>>> a significant latency difference
>>>  between Unix-domain sockets and FIFOs, since the interior kernel
>>> mechanisms are broadly similar.
>>>  Basically--some chunk of memory is copied from one place to another,
>>> there's some housekeeping, and
>>>  the system-call interface is traversed a couple of times.
>>
>> Let me contradict. Maximum latency is *much* better - less then 80us
>> instead of 3ms.
>>
>> Data attached as usual.  Tests were run with 'chrt 80 ./runtest_sh'
>>
>> PS I test on Core 2 Duo 1.6 GHz with all the GUI stuff running.
>
> Just did both tests on my machine here, Intel Core i5 notebook.
>
> I couldn't find such a high latency (3ms). Indeed, both are performing
> pretty much the same. I would even say that on my box, the pipe
> mechanism does even better in terms of jitter. I didn't calculate mean
> and standard deviation but from the plot it looks like the values are
> closer together.

So this once again means that there is no single answer. :)
We should put together a test which everyone could run and choose.


-- 
Regards,
Alexander Chemeris.