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depontius
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PostPosted: Thu May 22, 2014 10:43 pm    Post subject: Asus eee pc B202 [SOLVED] Reply with quote

So I've got Gentoo installed on this thing, and it's reasonable usable. No speed demon, but that's not to be expected. However before starting this venture I installed another gig of RAM, and ran it several days on memtest86+ to make sure it was good. At some point while waiting for stuff to compiler, I did a "free" and to my surprise saw:
Code:
$ free
             total       used       free     shared    buffers     cached
Mem:        900064     487748     412316      69752      33144     310524
-/+ buffers/cache:     144080     755984
Swap:      4095996          0    4095996

This thing is only using 1 gig. So today I emerged memtest86+ (I last ran it under a quickie xubuntu install.) and again watched it test 2G of RAM. Somehow Gentoo isn't seeing the whole 2G. I'm not sure what's up with this. One possible clue is found in /var/log/messages, but I don't know if it's a red herring, nor do I know how to correct it, if it's real:
Code:
May 21 06:13:39 localhost kernel: Expanded resource reserved due to conflict with PCI Bus 0000:00
May 21 06:13:39 localhost kernel: e820: reserve RAM buffer [mem 0x0009ec00-0x0009ffff]
May 21 06:13:39 localhost kernel: e820: reserve RAM buffer [mem 0x7f7a0000-0x7fffffff]

IIRC, that second line suggest a memory hole somewhere around the 1M line, but the third line might suggest a hole around the 1G line. Is it possible that RAM below 0x09ec00 (minor) and above 0x7f7a0000 (major?) are unusable due to conflicts with I/O space? Presumably this is correctable, and obviously memtest86+ didn't have any problem with it. Have I missed some sort of BIOS setting that memtest86+ ignored and Linux didn't?

Now that I think about it as I write this, I see:
Code:
CONFIG_NOHIGHMEM=y
# CONFIG_HIGHMEM4G is not set
# CONFIG_HIGHMEM64G is not set
CONFIG_VMSPLIT_3G=y
# CONFIG_VMSPLIT_3G_OPT is not set
# CONFIG_VMSPLIT_2G is not set
# CONFIG_VMSPLIT_2G_OPT is not set
# CONFIG_VMSPLIT_1G is not set

I don't remember dealing with these or tweaking them - I'll bet that they're stock settings. However I thought "HIMEM" was above 4G, and I thought VMSPLIT_3G meant 3G address space for userspace and 1G address space for the kernel. This doesn't look wrong to me.

Any insight?
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Last edited by depontius on Fri May 23, 2014 12:11 pm; edited 1 time in total
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khayyam
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Joined: 07 Jun 2012
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PostPosted: Fri May 23, 2014 12:57 am    Post subject: Re: Asus eee pc B202 Reply with quote

depontius wrote:
Code:
CONFIG_NOHIGHMEM=y
# CONFIG_HIGHMEM4G is not set
[...]

I don't remember dealing with these or tweaking them - I'll bet that they're stock settings. However I thought "HIMEM" was above 4G, and I thought VMSPLIT_3G meant 3G address space for userspace and 1G address space for the kernel. This doesn't look wrong to me.

depontius .... well, this is about address space and how the available RAM is accessed. If there is only 2gb of ram the kernel will still asign some to highmem and some to lowmem. Anyhow, in order to access the 2gb you have installed you need CONFIG_HIGHMEM4G=y ... the info from HIGHMEM4G states "Select this if you have a 32-bit processor and between 1 and 4 gigabytes of physical RAM" ... which you do.

best ... khay
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depontius
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PostPosted: Fri May 23, 2014 10:35 am    Post subject: Re: Asus eee pc B202 Reply with quote

khayyam wrote:
depontius wrote:
Code:
CONFIG_NOHIGHMEM=y
# CONFIG_HIGHMEM4G is not set
[...]

I don't remember dealing with these or tweaking them - I'll bet that they're stock settings. However I thought "HIMEM" was above 4G, and I thought VMSPLIT_3G meant 3G address space for userspace and 1G address space for the kernel. This doesn't look wrong to me.

depontius .... well, this is about address space and how the available RAM is accessed. If there is only 2gb of ram the kernel will still asign some to highmem and some to lowmem. Anyhow, in order to access the 2gb you have installed you need CONFIG_HIGHMEM4G=y ... the info from HIGHMEM4G states "Select this if you have a 32-bit processor and between 1 and 4 gigabytes of physical RAM" ... which you do.

best ... khay


Thanks. I've been out of practice on 32-bit kernel builds. I've been running 1 32-bit system for many years, but at this point it's just tweaking the prior kernel config, and I haven't touched that part of it in perhaps close to a decade. This is the first new 32-bit kernel in a long time. I'm rather surprised that the defaults were set that way.

Rebuilding kernel now, with HIGHMEM4G and VMSPLIT_2G_OPT. As slow as the disk is on this bugger, if I'm into swapping I'm as good as dead, anyway. The 3G/1G only buys me that, and it looks like the 2G/2G might give me even a squeak more usable RAM. We'll see, we can always change it.
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