Question about X on the arm's.

[Gene Heskett]

On Friday 25 November 2016 07:21:10 Boszormenyi Zoltan wrote:

> 2016-11-25 11:24 keltezéssel, Gene Heskett írta:
> > On Monday 21 November 2016 17:41:45 Gene Heskett wrote:
> >> Greetings X experts;
> >>
> >> I bought a monitor that should have been able to do 1920x1080p60Hz.
> >> One would expect thats a given when the card gets $140 lighter
> >> carrying it out past the RF stuff in Wallies front door frame, so I
> >> just bought 2 of the faster SBC's like the r-pi 3b but the one that
> >> will display what the r-pi 3b puts out, claimed to be a bit faster.
> >>
> >> It wasn't until I googled for its specs last night and discovered
> >> its max is 1366x768 that I actually got a picture out of it hooked
> >> to anything except the r-pi.
> >>
> >> My question has to do with the rendering and screen refresh rate,
> >> which is obviously about 1/4 of the speed an old single core, x86
> >> P4.
> >>
> >> I am assuming the X built for it is single threaded, and it could
> >> be made more pleasant to use if it scattered its jobs about the 4
> >> cores in the typical arm cpu.
> >>
> >> Is there a build switch that could accomplish this? This is a quad
> >> core 64 bit arm cpu, running at its default clock of 1.5GHz which
> >> it seems like should have the ponies to handle the load.  More heat
> >> sink maybe.
> >
> > Ping?
>
> Rasterman replied to you soon after your mail. See
> https://lists.x.org/archives/xorg/2016-November/058447.html

And which I somehow missed, but it is here, my apologies.

> >> Is there anything I can do, considering its only other job is
> >> serviceing the keyboard and rodent?
> >
> > I've since found, using htop, that X is not the heaviest cpu hog,
> > ssh is, about 3x that of X.
> >
> > What cipher is the least intensive cpu load? I've found these things
> > do not have telnet services installed.
>
> How about arcfour or one of its variants?
> On a trusted the LAN even a slow Geode LX can produce more than
> 100Mbit LAN bandwith. With more CPU intensive ciphers the speed
> is reduced to around 2MByte/sec.

I see by the listing of a -Q cipher that there several arc4's available.
On the raspi, running raspian:
gene at raspberrypi:/etc/ssh $ ssh -Q cipher
3des-cbc
blowfish-cbc
cast128-cbc
arcfour
arcfour128
arcfour256
aes128-cbc
aes192-cbc
aes256-cbc
rijndael-cbc at lysator.liu.se
aes128-ctr
aes192-ctr
aes256-ctr
aes128-gcm at openssh.com
aes256-gcm at openssh.com
chacha20-poly1305 at openssh.com

And on the odroid, running a 3 year older kernel:
3des-cbc
blowfish-cbc
cast128-cbc
arcfour
arcfour128
arcfour256
aes128-cbc
aes192-cbc
aes256-cbc
rijndael-cbc at lysator.liu.se
aes128-ctr
aes192-ctr
aes256-ctr
aes128-gcm at openssh.com
aes256-gcm at openssh.com
chacha20-poly1305 at openssh.com

So it looks like they match, but in making a choice, is there a url that 
discusses the relative merits of each, such as the cpu loading? In my 
case a well done report would simplify the choice & let me get back to 
the bigger picture.

I would assume that logging out, and restarting sshd from each machines 
keyboard, or a reboot of all involved would be required. I'll google for 
some docs, but just because it is security related, they seem to be 
squirreled away in darker corners.

Thank you very much.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
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Genes Web page <http://geneslinuxbox.net:6309/gene>