[gentoo-user] Linux too damn slow if memory > 3GB

[gentoo-user] Linux too damn slow if memory > 3GB

[Daniel van Ham Colchete]

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Hello everyone!!!

May be somebody can shed some light here... I'm building a server here with
4GB of RAM memory. The fact is, if I boot with mem=3072M everything goes as
fast as it should but I'm not using 1GB of memory. If I don't put the mem
option, Linux will see 4GB of memory available but it will be damn slow
(really).

To make Linux recognize 4 gigs of memory I had to activate HIGHMEM=64GB,
otherwise it only recognizes 3279MB (but it is fast).

My processor is a Intel Core 2 Duo E6320 (1.86Ghz). The motherboard is
Intel. I'm running Gentoo at 32bits mode and the kernel version is
2.6.20-gentoo-r8.

Any lights would be very appreciated.

Best regards,
Daniel Colchete

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Re: [gentoo-user] Linux too damn slow if memory > 3GB

[Tim Allingham]

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On Sat, 2007-07-28 at 20:28 -0300, Daniel van Ham Colchete wrote:
> Hello everyone!!!
> 
> May be somebody can shed some light here... I'm building a server here
> with 4GB of RAM memory. The fact is, if I boot with mem=3072M
> everything goes as fast as it should but I'm not using 1GB of memory.
> If I don't put the mem option, Linux will see 4GB of memory available
> but it will be damn slow (really). 
> 
> To make Linux recognize 4 gigs of memory I had to activate
> HIGHMEM=64GB, otherwise it only recognizes 3279MB (but it is fast).
> 
> My processor is a Intel Core 2 Duo E6320 (1.86Ghz). The motherboard is
> Intel. I'm running Gentoo at 32bits mode and the kernel version is
> 2.6.20-gentoo-r8.
> 
> Any lights would be very appreciated.
> 
> Best regards,
> Daniel Colchete

I don't actually run 4GB of RAM in any of my intel systems, so I can't
comment from experience, however my suspicion would be the overhead
introduced from PAE, which (at least on older kernels) requires some
processing overhead to utilise.  Are you able to try a 64-bit install to
determine if this is the case?

Regards,

Tim Allingham
Email:Tim@DataFirst-IT.com.au

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Re: [gentoo-user] Linux too damn slow if memory > 3GB

[Tim Allingham]

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On Sun, 2007-07-29 at 09:39 +1000, Tim Allingham wrote:
> On Sat, 2007-07-28 at 20:28 -0300, Daniel van Ham Colchete wrote:
> > Hello everyone!!!
> > 
> > May be somebody can shed some light here... I'm building a server here
> > with 4GB of RAM memory. The fact is, if I boot with mem=3072M
> > everything goes as fast as it should but I'm not using 1GB of memory.
> > If I don't put the mem option, Linux will see 4GB of memory available
> > but it will be damn slow (really). 
> > 
> > To make Linux recognize 4 gigs of memory I had to activate
> > HIGHMEM=64GB, otherwise it only recognizes 3279MB (but it is fast).
> > 
> > My processor is a Intel Core 2 Duo E6320 (1.86Ghz). The motherboard is
> > Intel. I'm running Gentoo at 32bits mode and the kernel version is
> > 2.6.20-gentoo-r8.
> > 
> > Any lights would be very appreciated.
> > 
> > Best regards,
> > Daniel Colchete
> 
> I don't actually run 4GB of RAM in any of my intel systems, so I can't
> comment from experience, however my suspicion would be the overhead
> introduced from PAE, which (at least on older kernels) requires some
> processing overhead to utilise.  Are you able to try a 64-bit install to
> determine if this is the case?
> 
> Regards,
> 
> Tim Allingham
> Email:Tim@DataFirst-IT.com.au

just to add, this page gives a reasonable explanation of the problems
with 32-bit OS's trying to address large RAM volumes

http://www.dansdata.com/askdan00015.htm

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Re: [gentoo-user] Linux too damn slow if memory > 3GB

[Daniel van Ham Colchete]

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On 7/28/07, Tim Allingham <deserted@westnet.com.au> wrote:
>
> On Sun, 2007-07-29 at 09:39 +1000, Tim Allingham wrote:
> > I don't actually run 4GB of RAM in any of my intel systems, so I can't
> > comment from experience, however my suspicion would be the overhead
> > introduced from PAE, which (at least on older kernels) requires some
> > processing overhead to utilise.  Are you able to try a 64-bit install to
> > determine if this is the case?
> >
> > Regards,
> >
> > Tim Allingham
> > Email:Tim@DataFirst-IT.com.au
>
> just to add, this page gives a reasonable explanation of the problems
> with 32-bit OS's trying to address large RAM volumes
>
> http://www.dansdata.com/askdan00015.htm
>
>
That is very very very sad...
The fact is I can't use 64bits for now... So let's take one gig out!
Thanks for your help!!!!

Daniel

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Re: [gentoo-user] Linux too damn slow if memory > 3GB

[Stroller]

On 29 Jul 2007, at 00:28, Daniel van Ham Colchete wrote:
> ...
> The fact is, if I boot with mem=3072M everything goes as fast as it  
> should but I'm not using 1GB of memory. If I don't put the mem  
> option, Linux will see 4GB of memory available but it will be damn  
> slow (really).
> ...
> My processor is a Intel Core 2 Duo E6320 (1.86Ghz). The motherboard  
> is Intel. I'm running Gentoo at 32bits mode and the kernel version  
> is 2.6.20-gentoo-r8.

Hi there,

Does your Intel motherboard feature the 945PM chipset?

I read about this last week:
http://listserver.themacintoshguy.com/pipermail/x4u/2007-July/ 
018031.html

Stroller.
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Re: [gentoo-user] Linux too damn slow if memory > 3GB

[Daniel van Ham Colchete]

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On 7/28/07, Stroller <stroller@stellar.eclipse.co.uk> wrote:
>
>
> On 29 Jul 2007, at 00:28, Daniel van Ham Colchete wrote:
> > ...
> > The fact is, if I boot with mem=3072M everything goes as fast as it
> > should but I'm not using 1GB of memory. If I don't put the mem
> > option, Linux will see 4GB of memory available but it will be damn
> > slow (really).
> > ...
> > My processor is a Intel Core 2 Duo E6320 (1.86Ghz). The motherboard
> > is Intel. I'm running Gentoo at 32bits mode and the kernel version
> > is 2.6.20-gentoo-r8.
>
> Hi there,
>
> Does your Intel motherboard feature the 945PM chipset?
>
> I read about this last week:
> http://listserver.themacintoshguy.com/pipermail/x4u/2007-July/
> 018031.html
>
> Stroller.
> --
> gentoo-user@gentoo.org mailing list
>
>

Stoller,

actually it's the 965, but the link Tim sent me shows that it's not a
chipset limitation... It's a 32bits design limitation...

Best,
Daniel

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Re: [gentoo-user] Linux too damn slow if memory > 3GB

[Steen Eugen Poulsen]

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Daniel van Ham Colchete skrev:
> actually it's the 965, but the link Tim sent me shows that it's not a
> chipset limitation... It's a 32bits design limitation...

Thats not true, I run 32bit Gentoo with 4 GB Memory and has no slowdown
issues I can measure with the naked eye.

Seems to me like you have some hardware problem.


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Re: [gentoo-user] Linux too damn slow if memory > 3GB

[Developer Edoceo]

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On 7/30/07, Steen Eugen Poulsen <sep@lix-world.net> wrote:
>
> Daniel van Ham Colchete skrev:
> > actually it's the 965, but the link Tim sent me shows that it's not a
> > chipset limitation... It's a 32bits design limitation...
>
> Thats not true, I run 32bit Gentoo with 4 GB Memory and has no slowdown
> issues I can measure with the naked eye.
>
> Seems to me like you have some hardware problem.



I have two Gentoo systems (2.6.x) one with 4G and another with 8G.  Both
systems are are wicked fast.  On the 4G `free` shows all but 21K of physical
used, on the 8G there's still 2G free and the system is highly responsive.
Can't remember which MB chipset I have, sorry.  multiple Intel multicore cpu
in both.

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Re: [gentoo-user] Linux too damn slow if memory > 3GB

[Daniel van Ham Colchete]

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On 7/30/07, Developer Edoceo <dev@edoceo.com> wrote:
>
> On 7/30/07, Steen Eugen Poulsen <sep@lix-world.net> wrote:
> >
> > Daniel van Ham Colchete skrev:
> > > actually it's the 965, but the link Tim sent me shows that it's not a
> > > chipset limitation... It's a 32bits design limitation...
> >
> > Thats not true, I run 32bit Gentoo with 4 GB Memory and has no slowdown
> > issues I can measure with the naked eye.
> >
> > Seems to me like you have some hardware problem.
>
>
>
> I have two Gentoo systems (2.6.x) one with 4G and another with 8G.  Both
> systems are are wicked fast.  On the 4G `free` shows all but 21K of physical
> used, on the 8G there's still 2G free and the system is highly responsive.
> Can't remember which MB chipset I have, sorry.  multiple Intel multicore cpu
> in both.
>

What kernel version are you using?

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Re: [gentoo-user] Linux too damn slow if memory > 3GB

[Duane Griffin]

On 29/07/07, Daniel van Ham Colchete <daniel.colchete@gmail.com> wrote:
> Hello everyone!!!
>
> May be somebody can shed some light here... I'm building a server here with
> 4GB of RAM memory. The fact is, if I boot with mem=3072M everything goes as
> fast as it should but I'm not using 1GB of memory. If I don't put the mem
> option, Linux will see 4GB of memory available but it will be damn slow
> (really).

It sounds like a problem with a buggy BIOS not setting up your MTRR
properly. This means linux ends up using ultra-slow memory for
important stuff. The problem has been discussed quite a bit on LKML,
see here, for example:

http://marc.info/?l=linux-kernel&m=118072237228294

> Any lights would be very appreciated.

Try upgrading to the latest BIOS version available for your
motherboard. If that doesn't fix it you will have to tell linux not to
use the affected memory. You can find out where that is by checking
your dmesg and /proc/mtrr, as described in the message referenced
above. Post the information here if you aren't sure.

Cheers,
Duane.

-- 
"I never could learn to drink that blood and call it wine" - Bob Dylan
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