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Re: [Discuss-gnuradio] Latency measurements with Unix-domain sockets
From: |
Andre Puschmann |
Subject: |
Re: [Discuss-gnuradio] Latency measurements with Unix-domain sockets |
Date: |
Tue, 31 May 2011 13:24:07 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110424 Lightning/1.0b2 Thunderbird/3.1.10 |
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