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Old 11-13-2007, 05:42 AM   #1
stokes
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Only 4Gb usable RAM when 8Gb physical is present


I have a few servers with more than 4Gb RAM installed, some have 8Gb and some have 12Gb. They were installed a few weeks ago.

The problem: I only have 4Gb of usable RAM on these servers. e.g.

[root@svhtbx03 2.6.9-55.0.12.EL-x86_64]# free -m
total used free shared buffers cached
Mem: 3945 830 3115 0 46 634
-/+ buffers/cache: 149 3795
Swap: 101 0 101

If I run top I also only see 4Gb available.

Mem: 4040040k total, 850372k used, 3189668k free, 47664k buffers

I want to use the x32 bit OS for compatibility, but I have also tried installing x64 bit just to see if it helped, but even with x64 I still only have 4Gb visible to the OS.

I have also tried installing kernel-hugemem and selecting it in the grub menu to boot from it, but even this makes no difference.

A few articles I have come across have suggested I need to configure a switch in the kernel to allow memory access up to 64Gb if I am using 4Gb, I will do this if I need to but I don't know now. When I look in make menuconfig, I can't find any option that looks like this.

Any suggestions are most welcome!
 
Old 11-13-2007, 05:53 AM   #2
Simon Bridge
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http://www.linux.com/feature/119287
... for 32 bit but the answer is the same. There is a kernel option to enable up to 64gig for RAM.

You need to set CONFIG_HIGHMEM64G to YES. And recompile.

If this is already enabled, then the kernel line in GRUB needs to include

mem=8192M for 8GiB and mem=12288M for 12GiB.
 
Old 11-13-2007, 07:53 AM   #3
stokes
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I don't have any HIMEM options in my Firmware Drivers section. This is what I have:

Firmware Drivers

<M> BIOS Enhanced Disk Drive calls determine boot disk (EXPERIMENTAL)│ │
<M> BIOS update support for DELL systems via sysfs │ │
<M> Dell Systems Management Base Driver │ │

This article says that the option was removed from menuconfig:

http://kerneltrap.org/node/6807

I did try selecting my processor typr first (Intel xeon).
 
Old 11-13-2007, 08:18 AM   #4
miedward
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You might check with the motherboard manifacturer and see if they have any updated linux drivers. Also check and see how much memory the BIOS sees, some boards have fairly arbitrary memory limits.
 
Old 11-13-2007, 08:28 AM   #5
vermaden
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Quote:
Originally Posted by stokes View Post
I don't have any HIMEM options in my Firmware Drivers section. This is what I have:

Firmware Drivers

<M> BIOS Enhanced Disk Drive calls determine boot disk (EXPERIMENTAL)│ │
<M> BIOS update support for DELL systems via sysfs │ │
<M> Dell Systems Management Base Driver │ │
Code:
# grep CONFIG_HIGHMEM64G /usr/src/linux/.config
# CONFIG_HIGHMEM64G is not set
use that to enable that option:
Code:
# sed -i -e s/"^.*CONFIG_HIGHMEM64G.*$"/CONFIG_HIGHMEM64G=y/g /usr/src/linux/.config
and recompile your kernel.
 
Old 11-14-2007, 07:00 AM   #6
stokes
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Quote:
Originally Posted by Simon Bridge
If this is already enabled, then the kernel line in GRUB needs to include

mem=8192M for 8GiB and mem=12288M for 12GiB.
This didn't make any difference by the way.

Quote:
Originally Posted by vermaden View Post
You might check with the motherboard manifacturer and see if they have any updated linux drivers. Also check and see how much memory the BIOS sees, some boards have fairly arbitrary memory limits.
I already checked that I'm afraid. I'm using the very latest firmware and RHEL drivers from HP. The BIOS indicates I do have the full 12Gb installed.

Quote:
Originally Posted by miedward
Code:
# grep CONFIG_HIGHMEM64G /usr/src/linux/.config
# CONFIG_HIGHMEM64G is not set
use that to enable that option:
Code:
# sed -i -e s/"^.*CONFIG_HIGHMEM64G.*$"/CONFIG_HIGHMEM64G=y/g /usr/src/linux/.config
and recompile your kernel.
OK - stop me if I am going wrong somewhere. This is what I've done :

Code:
up2date -i -f kernel-devel
cd /usr/src/kernels/2.6.9-55.0.12.EL-x86_64/
grep CONFIG_HIGHMEM64G .config
I don't get any output from the last command. I'm guessing this means the other command you gave me will not be able to set this flag.
 
Old 11-14-2007, 07:59 AM   #7
vermaden
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Quote:
Originally Posted by stokes View Post
I don't get any output from the last command. I'm guessing this means the other command you gave me will not be able to set this flag.
Its pretty old kernel (2.6.9) as for 2.6 series of course, so maybe there was no such option yet or maybe you just need to add CONFIG_HIGHMEM64G=y manually in .config?

I do not use Linux so much so more experienced users will tell you more.
 
Old 11-14-2007, 08:54 AM   #8
Simon Bridge
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grep CONFIG_HIGHMEM64G .config no output
... .config exists right?

check
grep CONFIG_HIGHMEM4G .config
grep CONFIG_NOHIGHMEM .config

up2date has newer kernels for you, surely?
 
Old 11-14-2007, 09:26 AM   #9
stokes
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Quote:
up2date has newer kernels for you, surely?
Well yes, but this kernel version is the recommended one for the application that runs on this server, I would prefer to stick to their guidelines as much as possible so that I won't have to arm wrestle with them to get support out of them further down the line

I've also just found this in my dmesg:

Code:
BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 000000000009f400 (usable)
 BIOS-e820: 000000000009f400 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000cfed70c0 (usable)
 BIOS-e820: 00000000cfed70c0 - 00000000cfee7ce8 (ACPI data)
 BIOS-e820: 00000000cfee7ce8 - 00000000d0000000 (reserved)
 BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved)
 BIOS-e820: 00000000fee00000 - 00000000fee10000 (reserved)
 BIOS-e820: 00000000ffc00000 - 0000000100000000 (reserved)
 BIOS-e820: 0000000100000000 - 000000032ffff000 (usable)
Warning only 4GB will be used.
Use a PAE enabled kernel.
3200MB HIGHMEM available.
896MB LOWMEM available.
I'm going to install kernel-hugemem now and select it from the grub menu and see what happens.
 
Old 11-14-2007, 09:35 AM   #10
stokes
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OK - eventually got to the bottom of it.

Booting using kernel-hugemem works. Now I just need to recompile my Qlogic FC drivers to work with this kernel.

Thanks all ... I am glad I didn't have to recompile the kernel, one job I have not done before and will continue to avoid for as long as possible!
 
Old 11-14-2007, 11:29 AM   #11
inspiron_Droid
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This is a common problem in any operating system be it windows, UNIX, Mac OS X or Linux but more so in Linux and windows because of built in lagacy support for mother boards that suppot less than 4gb or even les than a gigabyte of ram at the kernel level of thje OS as well as the Basic Inpout Output System (BIOS) Level which is the imbeded sofware on the main board that runs whe you forst boot up the machine and is also used to manage hardware intagration of PLug and Paly devices (Pnp) on boards thaty support PnP.
 
Old 11-14-2007, 08:58 PM   #12
Simon Bridge
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OT: linux-Hawk: I think you'll want to change your sig. dude. I'll explain:

Quote:
Originally Posted by linux-Hawk
October 2007 ISSUE 162 PG: 13
... from your sig.

Your link does not point to the article nor the issue.
http://www.linuxjournal.com/issue/162
... is the issue in question. Can't seem to find the article, did this make the online edition?

Anyway, I felt sure there was a mistake in the quote so I looked further.

Searching the issues shows the passages you quote are in a list of noteworthy quotes in the magazine. It's not really a Linux Journal story at all.

The original interview is online at All About Ubuntu, posted on June 26, 2007 by Len Sandy. The interview opens with:
Quote:
Sure, Dell is new to the Ubuntu PC market. But plenty of smaller PC suppliers have long supported Ubuntu. One prime example: ZaReason Inc., a PC maker made up of volunteers. I reached out to Cathy Malmrose, CEO of ZaReason, to get a feel for the company’s customer base and market position, and to get her views on Ubuntu’s longer-term prospects. Here’s a look at our conversation as it occurred over email.
Then follows the first question, which you have misquoted.
Quote:
Len (All About Ubuntu): How would you describe your customer base?

Cathy (ZaReason): Intelligent people.

You ask, “How can you siphon off only the most knowledgeable users as your customer base?” Good question; easy answer. Non-open source users typically use price as a factor in their decision. They think that a more expensive computer will be faster, more sturdy, and will last longer. That’s not necessarily true. It is definitely not true in software and it is becoming less true in hardware.

The more savvy users are attracted to our site because they recognize the actual parts we use and compare them to what other companies are using. They tend to be people fully in the FOSS mindset who have moved past the idea that cost = quality. We build high-end systems for a smaller price and they are capable of recognizing quality.
(My emphasis.)

Contrast this with your quote (at time of writing)
Quote:
Non-open-source users typically don’t use price as a factor in their decisions.
(My emphasis.)

The meaning is opposite, and, in your example, seems to build a negative impression (which, I suspect, you don't intend) when combined with the second part about "myopic". Myopic = short sighted - if I described something you did as "short sighted" you'd take offence, right?

But Cathy seems to intend the statement to be taken as a positive.
Quote:
Len (All About Ubuntu): How would you describe ZaReason’s business at this point? Are you still a start-up? A growing small business?

Cathy (ZaReason): We’re a growing small business with a business plan that is built to last. While we spent our careers in the trenches, we are now surrounded by Econ professors and PhDs here in Berkeley and get plenty of unsolicited advice on how to follow this unique business plan that is fully entrenched in FOSS principles. Our goal is to serve the open source community. Period. Focus. No other agendas.

We believe that all our other worthy goals (such as gaining market share for Linux) will be accomplished best by a myopic, utterly self-absorbed focus on solid hardware and honest customer support.
(My emphasis) See?

Perhaps she's trying to be ironical in her juxtaposition of "myopic, utterly self-absorbed" with "solid hardware and honest customer support". I suspect that the reply was edited, removing much of the context. Or maybe Cathy now wishes she'd chosen her words differently?

Conclusion:
Make sure your quote does what you intend - remember, you have read the whole thing and know the context. If you edit too much, the context is destroyed and the intended meaning can change.
Make sure a link attached to a quoted passage takes the reader to the actual passage. Not everyone is prepared or skilled enough to go hunting like I did.

Technically, I should be dropping this in private, so I apologize for any embarrassment I may have caused. However, the actual article makes some interesting points (as well as some neat predictions for Ubuntu to compare with what actually happened) so a public discussion could benefit the membership. 'Sides, some people may have got the wrong idea already - best try put them right eh?

If this discussion looks like it may become involved, I'll fork off another thread.

Feel free to tell me where to get off

Last edited by Simon Bridge; 11-14-2007 at 09:02 PM.
 
Old 11-16-2007, 06:14 AM   #13
salasi
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Quote:
But Cathy seems to intend the statement to be taken as a positive.
I think she was trying to highlight something summarised in the popular (if rather old fashioned) quote:

Quote:
A cobbler (or shoemaker) should stick to his last.
That is by not looking at into the wider field and getting distracted, you can do a better job. sometimes the potential disadvantage in this position has to be pointed out:

Quote:
A cobbler should stick to his last, but not so closely that he measures someone for skiing boots while they are wearing silk stockings.
In other words, while you do have to be a bit myopic to be an expert you can't be so myopic that you ignore the environment surrounding what you do (in this case that you'll actually wear thick woolly socks when skiing).

BTW: a last is what shoemakers use to make shoes on, in case the terminology is confusing anyone. (And my analogy has wandered way off topic, if anyone wants to terminate this thread.)
 
  


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