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Author Topic: Slowness with >4Gb of RAM on 32-bit kernel  (Read 3988 times)

Vanger

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Slowness with >4Gb of RAM on 32-bit kernel
« on: September 28, 2007, 09:37:37 am »

As I've seen 64Gb highmem option in kernel, I thought everything should be ok with >4Gb RAM support.
Now I've got 6Gb of RAM on my E6600 workstation and recompiled the kernel. Just changed 4Gb highmem to 64Gb, and all.
Whoa.
After reboot on new kernel system froze on udev start. Ok, I disabled udev, rebooted - well, my E6600 is as speedy as P2 233 could be on modern distro. I mean, I'm using twm as a window manager to get GUI for reasonable time now.
So I grabbed the latest kernel release (2.6.22.9). Cool, now it's like K6-2 400. And I'm supposed to run many virtual machines.
Can someone help with advice other then switch on 64-bit distro ;) ? I know about VL-5.9-pseudo, but it's kinda scary to use that on my production machine.
Motherboard is Intel on i965 chipset.
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Vanger

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Re: Slowness with >4Gb of RAM on 32-bit kernel
« Reply #1 on: September 28, 2007, 10:50:58 am »

Ok, victory is mine. Though palliative.
By trial and error found correct value to pass kernel - "mem=6770M". That gets me 6091Mbs of RAM. Yeah, I've lost 53Mb, but I'm too tired to experiment further.
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Joe1962

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Re: Slowness with >4Gb of RAM on 32-bit kernel
« Reply #2 on: September 28, 2007, 02:24:47 pm »

I would use mem=4096, because that's the limit addressable in 32 bit mode.
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Vanger

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Re: Slowness with >4Gb of RAM on 32-bit kernel
« Reply #3 on: October 01, 2007, 07:52:10 am »

No. I've said, I recompiled kernel with 64Gb highmem support.
Why should I use mem=4096 to loose 2Gb of RAM ;) ?
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Joe1962

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Re: Slowness with >4Gb of RAM on 32-bit kernel
« Reply #4 on: October 01, 2007, 02:52:19 pm »

Ok, so I've seen this switch in the kernel config, but thought it was something for special server hardware, or whatnot. But I've always wondered how this is supposed to work, when theoretically 32 bits of memory addressing tops out at 4GB? Never took the time to look it up though, guess it's Google time... ;D
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O'Neill (RE the Asgard): "Usually they ask nicely before they ignore us and do what they damn well please."
http://joe1962.bigbox.info
Running: VL 7 Std 64 + self-cooked XFCE-4.10