Messages in this thread | | | Date | Fri, 28 Sep 2007 17:40:23 -0600 | From | Robert Hancock <> | Subject | Re: General slowness with using 64Gb HIGHMEM option on 32-bit kernel |
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Sergey Popov wrote: > Short description: after recompiling 32-bit kernel with 64Gb highmem > support and rebooting into it, OS started working very much slower > then before. > > Specifications: Intel Core 2 Duo E6600@2,4Ghz on Intel i965Q-based > motherboard. 6Gb of DDR2 RAM, 2x1Gb+2x2Gb, dual-channel. > Vector Linux 5.8 (Slackware Linux 11-based), 2.6.20.3 kernel. > > Long description: after recompiling 32-bit 2.6.20.3 kernel with 64Gb > highmem option and rebooting into it, booting process froze on udevd. > After booting up from CD and disabling rc.udev, system started, but > it's work after rc.M script sarted was 5-10 times slower then usual. > top showed, that processes are taking much more CPU% time then usual. > I tried downloading the newest stable kernel - 2.6.22.9 - hoping, that > it would solve the problem. I downloaded it, booted from CD, and > compiled it with 64Gb highmem support. I felt some speed improvement, > but if on 2.6.20.3 machine performed like P166, now it is working like > P2-350. > I've found a similar problem, described on lkml - > http://lkml.org/lkml/2007/5/30/5 . But, unfortunately, it is x86_64 > related and contains no clues for me. > > Moving to 64-bit distro is rather unpleasant - as there is an option > in 32-bit kernel, it should work ;) . > > What tests should I run to help investigate this problem?
Make sure your BIOS is up to date. If so, post your dmesg output and the contents of /proc/mtrr. There are a number of Intel boards which have/had BIOS bugs where the BIOS didn't set up the MTRRs to mark all RAM as write-back. This results in the last bit of memory being uncacheable and causes a major performance drop.
-- Robert Hancock Saskatoon, SK, Canada To email, remove "nospam" from hancockr@nospamshaw.ca Home Page: http://www.roberthancock.com/
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