[HowTo] Enable High Memory support for kernel

chaosgeisterchen · 2008-04-17 22:59:37

Good evening!

This evening I filled up the vacant RAM slots in my PC and so I am now up to 6 GB of RAM. Nice thing to have, but Linux detects only around 3 GB of it.

free
             total       used       free     shared    buffers     cached
Mem:       3368244    1176192    2192052          0     107952     714320
-/+ buffers/cache:     353920    3014324
Swap:       506008          0     506008

I have read about changing the kernel config for High Memory support, but I do not really have an idea how to sustainably change the configuration of kernel26 to feature it. Can anyone explain to me in easy steps how to enable the High Memory support without installing Arch64 (which I will probably do anyway).

Thanks in advance
cg

brebs · 2008-04-17 23:20:27

"Easy steps"? This is not Ubuntu

It surprises me that seemingly so few Arch users compile their own kernel.

Anyway, to avoid PAE, reinstall (and yes you do need to *reinstall*, there is *no* upgrade path from arch32 to arch64) with Arch64.

lucke · 2008-04-17 23:39:13

Well, you could call those easy steps, courtesy of ABS.

Run abs, cd /var/abs/core/kernel26, edit config and enable HIGHMEM64G, remove/update md5sums in PKGBUILD and run makepkg. Voila.

chaosgeisterchen · 2008-04-17 23:44:07

Mea culpa. It seems as if I was searching for one 'too easy' way to solve the problem.

Compiling my kernel on my own is one of the many things I have never done - it somehow keeps me from attaining knowledge about Linux as a whole. As it seemingly is the only solution to do it using 32 bit, I will have to stick to it.

I know that there is no 'upgrade' option from Arch32 to Arch64, but since almost all packages are available and configs will stay the same I doubt that I will run into any major obstacles while re-installing.

cactus · 2008-04-17 23:56:00

chaosgeisterchen wrote:

Good evening!
This evening I filled up the vacant RAM slots in my PC and so I am now up to 6 GB of RAM. Nice thing to have, but Linux detects only around 3 GB of it.
free
             total       used       free     shared    buffers     cached
Mem:       3368244    1176192    2192052          0     107952     714320
-/+ buffers/cache:     353920    3014324
Swap:       506008          0     506008
I have read about changing the kernel config for High Memory support, but I do not really have an idea how to sustainably change the configuration of kernel26 to feature it. Can anyone explain to me in easy steps how to enable the High Memory support without installing Arch64 (which I will probably do anyway).
Thanks in advance
cg

Overview:
1. install abs, and sync
2. copy kernel pkgbuild to a location to edit it
3. modify config, and then build kernel
4. install kernel
5. edit pacman.conf to exclude kernel updates, so your kernel will not get autoreplaced.
6. enjoy your extra ram.

Details:
1. $ sudo pacman -Sy abs && sudo abs
2. $ cd ~; mkdir build; cp -a /var/abs/core/kernel26/ build; cd build
3. edit the file named 'config'
change the "CONFIG_HIGHMEM4G=y" line to "# CONFIG_HIGHMEM4G is not set"
change the "# CONFIG_HIGHMEM64G is not set" line to "CONFIG_HIGHMEM64G=y"
4. edit PKGBUILD file. increment the pkgrel value. delete the md5sum array (alternatively you can get the md5sum of the config file and replace the value in the list)
5. $ makepkg
then wait.. assuming build is successful, then continue..
6. $ pacman -U kernel26-*.pkg.tar.gz
7. edit /etc/pacman.conf
add "IgnorePkg = kernel26" under the [options] section.
8. reboot

Caveats:
Have a livecd handy on the off chance your system doesn't boot happily...so if you need to boot from a cd and manually mount and chroot to a partition to install the old kernel, you will be able to.
Also note that you will need to rebuild your kernel yourself whenever you want to update it, as the included arch kernels are not highmem64 enabled.

brebs · 2008-04-18 00:08:07

cactus wrote:

change the "CONFIG_HIGHMEM4G=y" line to "# CONFIG_HIGHMEM4G is not set"
change the "# CONFIG_HIGHMEM64G is not set" line to "CONFIG_HIGHMEM64G=y"

You fail. Have you looked at the top of /usr/src/linux/.config

# Automatically generated make config: don't edit

DON'T EDIT - use "make menuconfig" - but then that doesn't work with Arch's stupid kernel configuration, where "make menuconfig" fails.

This, and the /usr/share/doc/* deletion are the two biggest stupidities of Arch.

Edit: And secondly, Arch should be advising to use a fallback kernel, which is far better than requiring someone to stick in a boot CD.

Last edited by brebs (2008-04-18 00:14:51)

toofishes · 2008-04-18 00:34:39

brebs wrote:

cactus wrote:
change the "CONFIG_HIGHMEM4G=y" line to "# CONFIG_HIGHMEM4G is not set"
change the "# CONFIG_HIGHMEM64G is not set" line to "CONFIG_HIGHMEM64G=y"
You fail. Have you looked at the top of /usr/src/linux/.config
# Automatically generated make config: don't edit
DON'T EDIT - use "make menuconfig" - but then that doesn't work with Arch's stupid kernel configuration, where "make menuconfig" fails.
This, and the /usr/share/doc/* deletion are the two biggest stupidities of Arch.
Edit: And secondly, Arch should be advising to use a fallback kernel, which is far better than requiring someone to stick in a boot CD.

Leave. Seriously. You helped no one with this post. You hijacked someone elses thread to air your dirty laundry, of which none of the devs care about. You insulted one of my fellow devs, and it wasn't even legitimate. The config file IS a text file, just like any other. The directions were perfectly fine, actually.

You fail, and I hope you never have a feature request or bug report again, because no one on my side of the table cares about you anymore.

lucke · 2008-04-18 00:45:40

I feel my post was ignored :-( It was cactus who got insulted for proposing editing a config file, not me :-( I demand a refund! Or I'm leaving this distro in which menuconfig allegedly fails.

neotuli · 2008-04-18 00:47:41

brebs wrote:

cactus wrote:
change the "CONFIG_HIGHMEM4G=y" line to "# CONFIG_HIGHMEM4G is not set"
change the "# CONFIG_HIGHMEM64G is not set" line to "CONFIG_HIGHMEM64G=y"
You fail. Have you looked at the top of /usr/src/linux/.config
# Automatically generated make config: don't edit
DON'T EDIT - use "make menuconfig" - but then that doesn't work with Arch's stupid kernel configuration, where "make menuconfig" fails.

Oh dear. Kids and their language these days.
I'd also ask you to stop handing out advice when you have no idea what is going on, I've been told it's bad for your health. If you had actually read the PKGBUILD and ever configured a kernel in your life, you'd see that it runs something to the tune of "yes ''|config" in order to do any configuration manual editing of the file may have missed. Therefore, manually editing the kernel configuration and using arch's default PKGBUILD will not cause any harm. Your lack of knowledge also becomes aparent when you cite /usr/src/linux/.config, which could be any random old file. The most reliable configuration for your running kernel is always at /proc/config.gz.
Oh and uh.. thanks for the objective analysis of why it's "stupid".

brebs wrote:

This, and the /usr/share/doc/* deletion are the two biggest stupidities of Arch.

Is this relevant? It sounds like you're just here to start trouble...

brebs wrote:

Edit: And secondly, Arch should be advising to use a fallback kernel, which is far better than requiring someone to stick in a boot CD.

Or you know... we could assume you're intelligent (feel free to disagree with me) and competent enough (again, feel free to disagree) to be able to make your own decisions on this.

Misfit138 · 2008-04-18 02:37:26

We're all using the same distro for the same reason; because it's the best for us.
Lest we forget, we are all part of the Arch community and mutual respect must be pursued by all users. As I have repeated many times in the past, knowledgeable users and their posts are always appreciated, but I must encourage all to please share that knowledge amicably and respectfully. Let us also never forget, Arch is free, and is a community volunteer project.
Thread closed. (unfortunately)

Arch Linux

#1 2008-04-17 22:59:37

[HowTo] Enable High Memory support for kernel

#2 2008-04-17 23:20:27

Re: [HowTo] Enable High Memory support for kernel

#3 2008-04-17 23:39:13

Re: [HowTo] Enable High Memory support for kernel

#4 2008-04-17 23:44:07

Re: [HowTo] Enable High Memory support for kernel

#5 2008-04-17 23:56:00

Re: [HowTo] Enable High Memory support for kernel

#6 2008-04-18 00:08:07

Re: [HowTo] Enable High Memory support for kernel

#7 2008-04-18 00:34:39

Re: [HowTo] Enable High Memory support for kernel

#8 2008-04-18 00:45:40

Re: [HowTo] Enable High Memory support for kernel

#9 2008-04-18 00:47:41

Re: [HowTo] Enable High Memory support for kernel

#10 2008-04-18 02:37:26

Re: [HowTo] Enable High Memory support for kernel

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