[Bug 574733] Re: serve Xorg performance penalty due to [u]vesafb creating wrong PAT entries

Sun Jun 6 23:20:01 UTC 2010

Hi Jeremy,

today I tested the maverick alpha 1 and observed the same behavior as with lucid:
1. No extra kernel parameters:
  - vga16fb is loaded and not [u]vesafb
  - thus the framebuffer terminal does not work on my NC20 (maybe I should open a bug for this, too?)
  - no PAT entries are created by vga16fb
  - correct (write combining) PAT entries for "openchrome"
2. "video=vesafb:mtrr=3 vga=792" kernel parameter
  - vesafb is loaded
  - now the framebuffer terminal works correctly
  - "uncached-minus" PAT entries are created by vesafb
  - incorrect (uncached-minus) PAT entries for "openchrome"

Unfortunately the maverick alpha 1 ISO has no uvesafb in the initramfs,
so I couldn't test this.

I will upload the apport files while above config 2. is loaded.

Kind regards,
  Thomas

** Tags added: apport-collected

** Description changed:

  Hi,

  when using uvesafb or vesafb, these drivers will create uncached-minus
  PAT entries for the framebuffer memory because they use ioremap(). WHen
  the framebuffer memory intersects with the video RAM used by Xorg, the
  complete video RAM will be mapped uncached-minus what results in a
  server performance penalty.

  Here are the correct MTRR entries created by uvesafb:
  schlicht at netbook:~$ cat /proc/mtrr 
  reg00: base=0x000000000 (    0MB), size= 2048MB, count=1: write-back
  reg01: base=0x06ff00000 ( 1791MB), size=    1MB, count=1: uncachable
  reg02: base=0x070000000 ( 1792MB), size=  256MB, count=1: uncachable
  reg03: base=0x0d0000000 ( 3328MB), size=   16MB, count=1: write-combining

  And here are the problematic PAT entries:
  schlicht at netbook:~$ sudo cat /sys/kernel/debug/x86/pat_memtype_list 
  PAT memtype list:
  write-back @ 0x0-0x1000
  uncached-minus @ 0x6fedd000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee3000-0x6fee4000
  uncached-minus @ 0x6fee3000-0x6fee4000
  uncached-minus @ 0x6fee3000-0x6fee4000
  uncached-minus @ 0xd0000000-0xe0000000  <-- created by xserver-xorg
  uncached-minus @ 0xd0000000-0xd1194000  <-- created by uvesafb
  uncached-minus @ 0xf4000000-0xf4009000
  uncached-minus @ 0xf4200000-0xf4400000
  uncached-minus @ 0xf5000000-0xf5010000
  uncached-minus @ 0xf5100000-0xf5104000
  uncached-minus @ 0xf5400000-0xf5404000
  uncached-minus @ 0xf5404000-0xf5405000
  uncached-minus @ 0xf5404000-0xf5405000
  uncached-minus @ 0xfed00000-0xfed01000

  Therefore I created the attached patch for uvesafb which uses ioremap_wc() to create the correct PAT entries, as shown below:
  schlicht at netbook:~$ sudo cat /sys/kernel/debug/x86/pat_memtype_list 
  PAT memtype list:
  write-back @ 0x0-0x1000
  uncached-minus @ 0x6fedd000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee2000-0x6fee3000
  uncached-minus @ 0x6fee3000-0x6fee4000
  uncached-minus @ 0x6fee3000-0x6fee4000
  uncached-minus @ 0x6fee3000-0x6fee4000
  write-combining @ 0xd0000000-0xe0000000
  write-combining @ 0xd0000000-0xd1194000
  uncached-minus @ 0xf4000000-0xf4009000
  uncached-minus @ 0xf4200000-0xf4400000
  uncached-minus @ 0xf5000000-0xf5010000
  uncached-minus @ 0xf5100000-0xf5104000
  uncached-minus @ 0xf5400000-0xf5404000
  uncached-minus @ 0xf5404000-0xf5405000
  uncached-minus @ 0xf5404000-0xf5405000
  uncached-minus @ 0xfed00000-0xfed01000

  This results in a performance gain, objectively measurable with e.g. x11perf -comppixwin10 -comppixwin100 -comppixwin500:
  1: x11perf_xaa_lucid.log
  2: x11perf_xaa_lucid_patched.log

      1              2           Operation
  --------   -----------------   -----------------
  300000.0   296000.0 (  0.99)   Composite 10x10 from window to window 
   38400.0    38500.0 (  1.00)   Composite 100x100 from window to window 
    1760.0     1760.0 (  1.00)   Composite 500x500 from window to window 
  124000.0   202000.0 (  1.63)   Composite 10x10 from pixmap to window 
    3340.0    24400.0 (  7.31)   Composite 100x100 from pixmap to window 
     131.0     1150.0 (  8.78)   Composite 500x500 from pixmap to window 

  You can see the serve performance gain when composing larger pixmaps to window.
  Please consider applying/pushing the attached patch. I'll also attach a very similar patch for vesafb.

  Kind regards,
    Thomas
+ --- 
+ AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.22.1.
+ AplayDevices:
+  **** List of PLAYBACK Hardware Devices ****
+  card 0: VT82xx [HDA VIA VT82xx], device 0: ALC272 Analog [ALC272 Analog]
+    Subdevices: 1/1
+    Subdevice #0: subdevice #0
+ Architecture: i386
+ ArecordDevices:
+  **** List of CAPTURE Hardware Devices ****
+  card 0: VT82xx [HDA VIA VT82xx], device 0: ALC272 Analog [ALC272 Analog]
+    Subdevices: 1/1
+    Subdevice #0: subdevice #0
+ CRDA: Error: [Errno 2] No such file or directory
+ Card0.Amixer.info:
+  Card hw:0 'VT82xx'/'HDA VIA VT82xx at 0xf5400000 irq 51'
+    Mixer name	: 'Realtek ALC272'
+    Components	: 'HDA:10ec0272,144dc04e,00100001'
+    Controls      : 14
+    Simple ctrls  : 8
+ DistroRelease: Ubuntu 10.10
+ LiveMediaBuild: Ubuntu 10.10 "Maverick Meerkat" - Alpha i386 (20100602.2)
+ MachineType: SAMSUNG ELECTRONICS CO., LTD. NC20/NB20
+ Package: linux (not installed)
+ ProcCmdLine: BOOT_IMAGE=/casper/vmlinuz noprompt cdrom-detect/try-usb=true file=/cdrom/preseed/hostname.seed boot=casper initrd=/casper/initrd.lz video=vesafb:mtrr=3 vga=792 quiet splash --  priority=low debian-installer/language=de console-setup/layoutcode?=de
+ ProcEnviron:
+  LANG=de_DE.UTF-8
+  SHELL=/bin/bash
+ ProcVersionSignature: Ubuntu 2.6.34-5.13-generic 2.6.34
+ Regression: No
+ RelatedPackageVersions: linux-firmware 1.35
+ Reproducible: Yes
+ Tags: maverick kconfig needs-upstream-testing
+ Uname: Linux 2.6.34-5-generic i686
+ UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare
+ dmi.bios.date: 11/25/2009
+ dmi.bios.vendor: Phoenix Technologies Ltd.
+ dmi.bios.version: 10MQ
+ dmi.board.name: NC20/NB20
+ dmi.board.vendor: SAMSUNG ELECTRONICS CO., LTD.
+ dmi.chassis.asset.tag: No Asset Tag
+ dmi.chassis.type: 10
+ dmi.chassis.vendor: SAMSUNG ELECTRONICS CO., LTD.
+ dmi.chassis.version: N/A
+ dmi.modalias: dmi:bvnPhoenixTechnologiesLtd.:bvr10MQ:bd11/25/2009:svnSAMSUNGELECTRONICSCO.,LTD.:pnNC20/NB20:pvr04MQ:rvnSAMSUNGELECTRONICSCO.,LTD.:rnNC20/NB20:rvr:cvnSAMSUNGELECTRONICSCO.,LTD.:ct10:cvrN/A:
+ dmi.product.name: NC20/NB20
+ dmi.product.version: 04MQ
+ dmi.sys.vendor: SAMSUNG ELECTRONICS CO., LTD.

-- 
serve Xorg performance penalty due to [u]vesafb creating wrong PAT entries
https://bugs.launchpad.net/bugs/574733
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