X performance woes

Marius Gedminas marius at pov.lt
Sun Apr 19 14:15:52 UTC 2009


On Sat, Apr 18, 2009 at 04:34:34PM -0400, Hal Burgiss wrote:
> After upgrading to 8.10 I am still having awful X performance issues.

What's your hardware?

The most relevant bit would be the video card (lspci -nn |grep VGA).

Also relevant could be your /etc/X11/xorg.conf and /var/log/Xorg.0.log.

> The worst is of course in Firefox, but I have very similar problems if
> I switch to Opera, so its not just Firefox. And its not just my system
> since most of this is just since the upgrade. Can anyone explain why
> simply *typing* in a browser text field can consistently spike the CPU
> to 100%.

Because the video driver is buggy and is doing much more work than is
necessary to draw the text you've just typed.

> Its close to unusuable. I am reluctant to scroll pages, as I
> will enter the land of "watching paint dry" while the load triggered
> case fan sounds like its in a nascar race. 

Ouch.

> Noothing happening now, normal process list:
> 
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                  
>  8887 halb      20   0  381m 226m  24m S  3.8 22.6  10:36.79 firefox                                  
> 13548 root      20   0  423m  62m 7320 S  3.8  6.2 663:33.21 Xorg                                     

What's your uptime?

With an uptime of 1 day, 20:28, I have here

 4981 mg        20   0  466m 303m  19m R   15 15.4  82:41.66 firefox                                                                                         
 3692 root      20   0  498m  61m  48m R   14  3.1  68:15.20 Xorg                                                                                            

which means X burned 68 minutes of CPU time during those 44 hours, so
it's average CPU usage is 2.5%.  Low enough---as you can see, Firefox
used up more CPU than X.

Technically, it's not uptime that's relevant, but the duration of your
current login session.  I tend to login as soon as I boot, and I launch
Firefox as soon as I login, so in my case those numbers should be
accurate.

> Now, a minute later while typing in a text field (twitter.com):
> 
>  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                  
> 13548 root      20   0  423m  62m 7320 R 51.1  6.2 663:34.85 Xorg                                     
>  8887 halb      20   0  381m 226m  24m R 47.1 22.6  10:38.51 firefox                                  

Ouch.

Sysprof or oprofile could help pinpoint the cause of the problem, but
first it might be simpler to see if you're using the right X video
driver with the right options, and for that we need to see your
xorg.conf and Xorg.0.log.

> That load is from the *keyboard*. Madness! It stays like that until
> after I stop typing. I have disabled addons, changed config settings,
> etc, but it does not help significantly.

Perhaps you haven't been changing the right config settings.

Also, do you use desktop effects (that is, Compiz)?

> Opera is just as bad so I
> don't think its just Firefox bloat.

Definitely not.

> Epiphany if anything is worse. I
> switched from gnome to xfce and that helped greatly with some
> performance issues, but something is still right royally fubared. 

So it is.

For me, with intel video on a 965GM, performance was OK in Hardy,
slightly degraded but acceptable in Intrepid, very bad with the default
settings in Jaunty.  After I switched to a different acceleration method
(UXA), as described in Jaunty's release notes, the performance is now
slightly worse than in Intrepid but still acceptable, at the cost of
some stability issues (which are smaller than the stability issues I had
in Intrepid when using multiple screens).

I understand that the intel video developers are very busy laying the
groundwork for improved features and performance, and that performance
may temporarily suffer while they're doing that work.  (For values of
"temporarily" measured in years.)  Ubuntu X.org maintainers are trying
very hard to bring those advanced features to the users while at the
same time choosing the right set of default options to make the
performance still acceptable.  They need useful feedback from their
users and testers, so if you could attach your xorg.conf and Xorg.0.log,
I'm sure they'd be grateful.

Marius Gedminas
-- 
The *REAL* Y2K is the year 2048.
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