Question about X on the arm's.

[Antoine Martin]

On 29/11/16 07:57, Carsten Haitzler (The Rasterman) wrote:
> On Mon, 28 Nov 2016 17:03:17 -0500 Gene Heskett <gheskett at shentel.net> said:
> 
>> On Monday 28 November 2016 13:12:03 Alan Coopersmith wrote:
>>
>>> On 11/27/16 04:29 PM, Gene Heskett wrote:
>>>> Okay Alan, I've had 3 or 4 folks over the last 36 hours claim that X
>>>> is its own forwarding agent, why am I even using ssh? saying I'm not
>>>> needing ssh at all.
>>>
>>> X can connect directly, but without the encryption & compression that
>>> ssh adds when it acts as the forwarding agent.  ssh has been the
>>> modern recommended solution for years - all major distros have started
>>> X with "-nolisten tcp" for over a decade, and recent versions of Xorg
>>> made that the default, such that you need to go specify "-listen tcp"
>>> to enable the old direct TCP connection method now if you want to
>>> avoid ssh.
>>>
>>>> So, where can I find the definitive tut on doing this because our
>>>> attempts are failing?  What I was able to find on the xorg web pages
>>>> last night was up to 3 major versions out of date.  I need a tut
>>>> that deals with X11R7 and up.  Is there such a thing?  My google-fu
>>>> is failing me.
>>>
>>> Our recommendation for X11R7 remote connections is "Use SSH X11
>>> Forwarding."
>>>
>> Which works but at very lethargic speeds. 3, 4 frames a second.  I need 
>> 20 or more. This odroid64, with at least 3 gpu's is said to be able to 
>> do a 4k display at 60 frames a second.
> 
> that'd be simply display REFRESH. not actual rendering of content. and forget
> REMOTE display over ssh over a bottleneck of a network device. forget trying to
> get anything like high performance over a network connection when it comes to
> display. don't even bother. it's a waste of time.
I beg to differ. An arm CPU certainly makes this more of a challenge,
but it is not a lost cause... just don't use SSH forwarding, some tuning
IS required.

> if it displays at ALL - be
> happy. to provide updated pixels at 60hz for a 4k display would require a
> 16 GIGABIT network... with NO OTHER TRAFFIC on it at all. and no network
> packet/protocol overhead. so let's make that 20 gigabit. that's assuming
> xputimage with 24bpp images (padded out to 32bpp as that's how xputimage
> works). that does not account for bottlenecks outside the network itself (the
> system at either end and it's tpc/ip stack, kernel, memcpy's etc. etc.).
I don't think the OP is trying to watch a 4K video over TCP, rather
stating that his hardware is capable of pushing 4k at 60 pixels, which is
why he was expecting better results.

If you exclude the 4k fullscreen video use case - which is a worst case
scenario for remote display (there are tricks to deal with that too if
you are willing to make sacrifices), then screen updates are actually
much more manageable, even on a 1Gbps shared link.

Cheers
Antoine


> 
>>> Unfortunately, so few people are willing to help write X11 docs that
>>> there isn't a whole lot of stuff written since the X Consortium
>>> stopped paying doc writers in the mid 90's.
>>
>> Yikes! NDW I cannot find uptodate docs & tuts.
>>
>> Thanks Alan, I appreciate the candor.
>>
>> Cheers, Gene Heskett
>> -- 
>> "There are four boxes to be used in defense of liberty:
>>  soap, ballot, jury, and ammo. Please use in that order."
>> -Ed Howdershelt (Author)
>> Genes Web page <http://geneslinuxbox.net:6309/gene>
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