[Bug 816035] Re: Memory upgrade makes Ubuntu painfully slow

[Andy Whitcroft]

I am suspicious that the following mtrrs though reasonable looking are
actually the issue:

[    0.000000] MTRR variable ranges enabled:
[    0.000000]   0 base 000000000 mask F80000000 write-back
[    0.000000]   1 base 07E800000 mask FFF000000 uncachable
[    0.000000]   2 base 07F800000 mask FFF800000 uncachable
[    0.000000]   3 base 07E700000 mask FFFF00000 uncachable

Note that 1 and 2 overlap, this is normally a situation which triggers
'undefined' behaviour including doing utterly the wrong thing.  We
should try booting with enable_mtrr_cleanup and see if that helps any.

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https://bugs.launchpad.net/bugs/816035

Title:
  Memory upgrade makes Ubuntu painfully slow

Status in NULL Project:
  Invalid
Status in “grub2” package in Ubuntu:
  New
Status in “linux” package in Ubuntu:
  Confirmed

Bug description:
  When upgrading the system memory of an Acer Veriton 1000 from 1GB to
  2GB, the Ubuntu 11.04 operating system becomes unusable slow. The
  problem is reproducible and only occurrs when both memory modules are
  inserted (operation in dual-channel mode). When booting from the live
  CD the problem does not occur, only when booting the operating system
  from hard disk after installation. When booting from the live CD, the
  hard drive can also be mounted and accessed with normal performance.

   The following diagnostic steps have already been performed:

  - upgraded system BIOS to latest version available
  - tried different memory modules (same outcome)
  - run memtest86 (all memory ok)
  - run ubuntu and other Linux from live CD (works ok)
  - installed Windows XP on hard drive (boots and runs with normal performance)
  - installed Fedora Linux 15 on hard drive (boots and runs with normal performance)

  More information:
  - Performance is already very slow at the Ubuntu Grub Bootloader Menu (before OS kernel is loaded): takes about 20 seconds to draw the main screen, 20 more seconds to draw the edit screen when using "e" button on a grub list element
  - Besides the very poor performance no errors are shown; OS can also be booted in about 10mins (instead of 30 seconds when only one mem module is inserted)
  - When OS is booted, bottleneck seems to be disk I/O, but hard disk activity is only very low; no kernel / system errors visible, system responsiveness also ok as long as no disk access happens.

  I suspect Ubuntu to apply some special settings already at GRUB
  bootloader level when installing to a hard drive, or access memory in
  a special way. These "settings" seem not to be compatible with the
  systems dual channel memory access mode.

  Please inform me when any additional information is required, I'll be
  glad to provide.

  Kind regards,
  H.

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