On 6/6/2013 3:24 PM, Sebastian Kuzminsky wrote:
> On 6/6/13 13:19 , Kent A. Reed wrote:
>> My interest has been tweaked by several remarks made about performance
>> on the BeagleBone Black. I've started a page
>> (https://sites.google.com/site/manisbutareed/beaglebone-black-linuxcnc)
>> and to kick it off posted some gross characterizations of the burden
>> imposed by various LinuxCNC GUIs and use of SSH/X11 Forwarding.
>>
>> This has been a little something to keep me busy in the wee hours....
>>
>> Regards,
>> Kent
>>
>> PS - I'm not a fan of the comment mechanism so it is disabled on my
>> site. Emails to me or the list will do.
> It's interesting that ssh for the X forwarding is a big chunk of your
> CPU utilization. Have you tried switching ssh form the default 3des
> cipher to blowfish? It's much faster.
>
>
There's more to come in the details that I haven't posted yet. Despite
blowfish and arcfour both being faster---it must be true, I read it on
the Internet---they don't substantially aid here. The issue may be
clouded by the ARM chip which I suspect isn't tweaked the way many x86
chips are, and the algorithms in the OpenSSH routines, which I suspect
may have been tweaked for x86. There were differences to be sure, just
no home runs.
The ciphers I forced my SSH client to select using the -c option were
-c (default) aes128-ctr
-c arcfour256
-c arcfour128
-c arcfour
-c blowfish-cbc
I also ran throughput tests between the hosts, using 'dd' to generate
very large files of zeros in memory (to avoid benchmarking the file
system) on the BBB and piping them through ssh to one of the x86 hosts.
Haven't had time to post the numbers.
I did not see any significant advantage to using compression (-C
option), either. That's a technique often used in WAN communcations,
whereas my hosts are communicating over a single LAN segment.
Regards,
Kent
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