[Gllug] Re: Alcatel SpeedTouch on Slackware 10

[Nix]

On Fri, 18 Nov 2005, Henry Gilbert gibbered uncontrollably:
> All fixed now. Just need an init script. glxgears FPS 272 which was
> what I was aiming for on this piece of relic. I have to admit this
> kernel 2.4.31 was recompiled very fat; and the difference in speed
> between a previous very slimmed version is pretty imaginary. I can't
> tell and I wouldn't know the best way to benchmark it anyway. Just

Optimizing the kernel for greater speed by recompiling it is pretty much
a waste of time. Most kernel subsystems have zero impact on the speed of
other subsystems (the kernel is highly modular, and keeps itself in one
big page so making the kernel bigger doesn't even lead to TLB
thrashing). Under normal loads most systems spend most of their time
*sleeping* or waiting for disk I/O or other such things in the kernel:
the CPU load of the kernel is really very low, even with HZ=1024.

Your glxgears speedup was almost certainly caused by compiling the
AGP and DRM stuff; perhaps it wasn't built before. Without that, the
card's 3D facilities will be basically unused.

See (as you probably know but I'll say it anyway),

glxinfo | grep direct

(obviously direct rendering only works with local X clients; if they're
running over the network they will *not* be able to talk directly to
the video hardware in the local machine!)

> noticed Debian Gnome crawling versus fast KDE 3.4 Slackware whizzing
> in this case.

Crawling under what load?

(One tool that is really *very* useful in this sort of situation is
<http://oprofile.sf.net/>, which lets you profile the *entire system*
looking for hotspots. Of course you need to be able to understand
and speed up the slow code in order for oprofile's output to be any
use at all...)

-- 
`Y'know, London's nice at this time of year. If you like your cities
 freezing cold and full of surly gits.' --- David Damerell

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