Re: Why is IceCat/GuixSD slower than Firefox/Debian on headless servers?

[Vladimir Sedach]

> Running from a desktop to a headless server, and based on side-by-side
> clicking, IceCat/GuixSD takes ~5x times as long as Mozilla/Debian to
> respond to clicks. Further, Mozilla/Debian takes ~5x times as long as
> Mozilla running on the desktop. The bottom line: IceCat/GuixSD is
> unbearably slow.
>
> Has anyone else seen this?
>
> Is there a known IceCat/GuixSD performance problem?

This sounds like an X11 protocol issue. Starting with Firefox 47,
XRender support is disabled by default:

https://www.reddit.com/r/firefox/comments/4nfmvp/ff_47_unbearable_slow_over_remote_x11/

Basically newer versions of Firefox stop using X11 correctly because
Mozilla considers X11 "technical debt," and because X11 does not support
some kinds of graphics acceleration.

Back when Wayland development started the popular ideology became that
no one needed or wanted remote graphics, if you want it use desktop
forwarding like VNC, else tough luck. A lot of people bought into that
and now we are seeing the results.

Check the value of gfx.xrender.enabled in about:config and try turning
it on/off to see if that changes the performance. It should come enabled
in Firefox 45, and is probably disabled in the newer IceCat.

If it is lack of XRender causing the problems, the more interesting
question is why running Firefox 45 remotely is so much slower than
running it on the desktop. You can try VNC forwarding to see if it is
some other X11 issue. Make sure to get Firefox 45 on the desktop for a
valid comparison.

Vladimir