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

[Andre Puschmann]

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.

Cheers,
Andre