Bug 22358

Summary: Performance regression: Sluggish text scrolling, 100%CPU after upgrade from 2.7.1 (UXA bug)
Product: xorg Reporter: Bryce Harrington <bryce>
Component: Driver/intelAssignee: Gordon Jin <gordon.jin>
Status: RESOLVED FIXED QA Contact: Xorg Project Team <xorg-team>
Severity: major    
Priority: high CC: cjwatson, lool
Version: 7.4 (2008.09)   
Hardware: x86 (IA32)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
Screenshot.png
none
BootDmesg.txt
none
CurrentDmesg.txt
none
XorgLog.gz none

Description Bryce Harrington 2009-06-18 19:38:17 UTC 
Created attachment 26934 [details]
Screenshot.png

Forwarding this Ubuntu bug report:
https://bugs.edge.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/388368

[Problem]
Poor performance experienced with text scrolling and text typing when using 2.7.99.x, along with incorrectly colored letters.  Issue goes away downgrading to 2.7.1.

[lspci]
00:00.0 Host bridge [0600]: Intel Corporation Mobile PM965/GM965/GL960 Memory Controller Hub [8086:2a00] (rev 0c)
	Subsystem: Dell Device [1028:01fe]
00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller [8086:2a02] (rev 0c)
	Subsystem: Dell Device [1028:01fe]

[RelatedPackageVersions]
 xserver-xorg 1:7.4~5ubuntu21
 libgl1-mesa-glx 7.4.1-1ubuntu2
 libdrm2 2.4.11-0ubuntu1
 xserver-xorg-video-intel 2:2.7.99.1+git20090602.ec2fde7c-0ubuntu2
 xserver-xorg-video-ati 1:6.12.2-2ubuntu1

[System]
 Architecture: i386
 Date: Wed Jun 17 10:47:29 2009
 DistroRelease: Ubuntu 9.10
 MachineType: Dell Inc. Latitude D830
 ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.30-9-generic root=UUID=6df978ed-c024-49d7-9157-bdd7bd05153d ro quiet splash
 distro: Ubuntu
 architecture: i686kernel: 2.6.30-9-generic
 dmi.bios.date: 06/07/2007
 dmi.bios.vendor: Dell Inc.
 dmi.bios.version: A02
 dmi.board.name: 0HN341
 dmi.board.vendor: Dell Inc.
 dmi.chassis.type: 8
 dmi.chassis.vendor: Dell Inc.
 dmi.modalias: dmi:bvnDellInc.:bvrA02:bd06/07/2007:svnDellInc.:pnLatitudeD830:pvr:rvnDellInc.:rn0HN341:rvr:cvnDellInc.:ct8:cvr: 
dmi.product.name: Latitude D830
 dmi.sys.vendor: Dell Inc.

[Original Report]
Versions of the Intel driver later than 2:2.7.1-1ubuntu1 are unusably slow for me. The first thing I do after starting X is normally to start a pterm and maximise it; the first sign of trouble is that the scrollbar takes ages to be replaced by normal black terminal area on maximisation. After that, Xorg is using nearly 100% CPU, text scrolling is very slow, etc. Typing this report is excruciatingly painful because it can take up to a second for each character to appear, especially when the typeahead buffer gets at all full.

EXA vs. UXA makes no obvious difference.

There are some rather odd visual effects as well: lots of letters are the wrong colour. This may have only started after switching VT away from X and back; I'm not quite sure. Bizarrely, this is visible in a screenshot (I'm not using compiz or anything fancy like that), which I'll attach to this bug.

Downgrading to 2:2.7.1-1ubuntu1 puts everything back to normal.
Comment 1 Bryce Harrington 2009-06-18 19:42:07 UTC 
Created attachment 26935 [details]
BootDmesg.txt
Comment 2 Bryce Harrington 2009-06-18 19:42:28 UTC 
Created attachment 26936 [details]
CurrentDmesg.txt
Comment 3 Bryce Harrington 2009-06-18 19:46:40 UTC 
Created attachment 26937 [details]
XorgLog.gz
Comment 4 Eric Anholt 2009-06-18 20:21:44 UTC 
Tried pterm here, and it's slow because it's using core text (lame software), but not outrageously slow like you describe.

From the dmesg, your kernel config appears to be broken and including the DRM built in, but not AGP support.  Sadly, Kconfig appears to allow this at the moment.
Comment 5 Colin Watson 2009-06-19 04:22:15 UTC 
You might be using the last officially-released version of pterm. It does have support for client-side fonts in the version I'm using (from svn; they need to get round to making a release); I'm just used to server-side fonts and haven't got round to changing over yet.

If missing agpgart is the problem, then I suspect that it might actually be more directly the fault of my /etc/modules, which had 'i915 modeset=1' but no drm or agpgart. I've adjusted this per some more current directions in https://wiki.ubuntu.com/X/KernelModeSetting, and will give that a go at my next reboot. Thanks!
Comment 6 Colin Watson 2009-06-19 06:48:50 UTC 
Making sure that intel_agp and drm (thereby agpgart) are loaded before i915 definitely seems to have cleared this up so far. Thanks for the suggestion.
Comment 7 Eric Anholt 2009-06-23 09:41:10 UTC 
commit 8c52da503b7e4cf961807f11824e3258ef9f7f1c
Author: Eric Anholt <eric@anholt.net>
Date:   Thu Jun 18 20:22:19 2009 -0700

    drm/i915: Add missing dependency on Intel AGP support.
    
    Users could accidentally enable AGP but not the Intel AGP support, and get
    a DRM that doesn't probe as a result.
    
    Bug #22358.
    
    Signed-off-by: Eric Anholt <eric@anholt.net>

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