Subject: Re: bug#8248: 23.2; Emacs 23.2 very slow over ssh when vertical-scroll-bar is enabled

From: Stefan Monnier <[email-masked]>
Date: Mon, 14 Mar 2011 21:40:19 -0400

> When vertical-scroll-bar is enabled on emacs 23.2 and used over ssh -X
> then switching buffers (^X ^B) takes several seconds. Likewise
> scrolling, changing windows etc. is very sluggish. I have a 12/5 Mbps
> cable line between work/home with usually 8-12ms ICMP rtt. Plenty of
> available bandwidth and CPU.

This will depend on the kind of vertical scollbars you're using.
The bug-data you sent indicates you're using a Gtk build, so it may also
depend on the theme you're using.

Do you see similar problems when running other Gtk applications over
this "ssh -X" tunnel?

> When googling 'emacs ssh latency' there seems to be more people
> having this problem and the prevalent advise was to use use server
> fonts and not client fonts. I tried to compile emacs with

I have no first hand knowledge of how server-side fonts compare to
client-side fonts, but according the some influential X11 hacker,
client-side fonts may actually be better because the bandwidth required
to send the chars's bitmaps is not significantly higher than the font
metrics that the client otherwise has to download from the server, but
sending the bitmaps can be streamed and is latency tolerant whereas
requesting the font metric tends to suffer from a lot of
round-tripping.

        Stefan