Re: [gentoo-user] weird 4GB RAM and kernel issue

[Rick van Hattem]

On Sunday 02 April 2006 02:04, kashani wrote:
>       I've made my problem go away, but I'm a bit curious about why it was
> happening.
>
> I've got nine or so Dell 1850's with 2 x 2GB chips. When I compile
> gentoo-source 2.6.15-r1 (and 2.6.14-r5) with support for 4GB I see only
> 3GB. 1GB lowmem and 2GB highmem.
>
> ws04 ~ # cat /proc/meminfo
> MemTotal:      3107408 kB
> MemFree:       1731660 kB
> Buffers:        219720 kB
> Cached:         937980 kB
> SwapCached:          0 kB
> Active:         455100 kB
> Inactive:       717924 kB
> HighTotal:     2227968 kB
> HighFree:      1271588 kB
>
> When I recompile on the same hardware with support for 64GB RAM I see
> the full 4GB in the usual 1GB/3GB split.
>
> nms02 ~ # cat /proc/meminfo
> MemTotal:      4147776 kB
> MemFree:       3762712 kB
> Buffers:        151404 kB
> Cached:          45116 kB
> SwapCached:          0 kB
> Active:          56724 kB
> Inactive:       145000 kB
> HighTotal:     3276544 kB
> HighFree:      3222936 kB
>
> However on my HP DL360 with 4 x 1GB RAM I see the 4GB, though it's a bit
> smaller, with 4GB enabled in the kernel. Same kernel version as the Dell's.
>
> [EMAIL PROTECTED] ~ $ cat /proc/meminfo
> MemTotal:      3977744 kB
> MemFree:        116792 kB
> Buffers:        296108 kB
> Cached:        3157952 kB
> SwapCached:          0 kB
> Active:        2725152 kB
> Inactive:       782956 kB
> HighTotal:     3096552 kB
> HighFree:         8680 kB
>
> I've been Googling around for an explantion, but am not really sure what
> I'm looking for. I'd assume that I might lose a few hundred MB if the 2
> x 2GB chips are slightly bigger than the 4GB limit rather than the full
> 1GB that seems to disappear. I'm guessing some wacky motherboard
> interleaving thing where highmem ends up being one chip and the lowmem
> the 896MB on the other chip.
>
> Anyone have a decent theory on this with a nice link?
>
> kashani
Enabling 4GB support instead of 1 will allow < 4GB of ram, _not_ <=4GB.
To be sure you can use all of it you have to select 64GB at the kernel.

The reason it does work for your DL360 is because the bios works around the 
problem for you.

-- 
Rick van Hattem Rick.van.Hattem(at)Fawo.nl

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