[Bug 54635] slow overall performance (because of highmem support and/or AGP settings?)

Michael Tinsay tinsami1 at yahoo.com
Mon Nov 6 10:08:52 UTC 2006

Public bug reported:

I have a P4 1GB system.  Part of the memory is shared with the built-in AGP card.  The BIOS is setup to have a 32MB AGP Aperture.

Problem:  When the Memory Allocated to the AGP Card is 16MB (lower than
the aperture setting)  Ubuntu is very sluggish, like it takes 5 whole
minutes to boot up.  But:

(1)  When the shared memory is at 32MB, Ubuntu is very fast -- 30 seconds from boot to KDM login screen.
(2)  When shared memory is at 16MB and kernel parameter mem=992M is used, Ubuntu is fast. But when mem=1008M is used, performance goes back to "snail" mode.
(3) When using latest available Dapper kernel source (Package Linux-Source-2.6.15), compiled without highmem support, performance is fast.


(1) Problem not encountered with Windows XP (with 32MB aperture and 16MB shared memory)
(2) Problem have been tested to latest available kernels from Breezy, Dapper, and even, Edgy.

Not really a big problem, but should this behavior, once confirmed, should be documented somewhere.  There's a lot of people complaining about slow performance in ubuntuforums.org, this may be one of the culprit.

** Affects: linux-source-2.6.15 (Ubuntu)
     Importance: Undecided
         Status: Unconfirmed

slow overall performance (because of highmem support and/or AGP settings?)

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