[SOLVED] Total memory being reported incorrectly

l0rddarkf0rce · 01-20-2011, 12:26 PM

Hello all, I'm running 13.1 on a Dell Latitude D630 with 4GB of RAM. My problem is that Slackware doesn't seem to see all of the available memory. Here are the #s being reported (just including pertinent #s rather than all output)...

Code:

free -m

   total: 3546
   used : 1003
   free : 2543

Code:

top
   Mem: 3631764k total, 1020544k used, 2611220k free

Code:

SuperKaramba
   Total Memory: 3547 MB

Code:

demicode -t memory

   Physical Memory Array
      Maximum Capacity: 4 GB

   Memory Device
      Size: 2048 MB

   Memory Device
      Size: 2048 MB

By reading the output of demicode I can see that the BIOS is reporting the correct amount available, but for some reason the rest of the applications seem to only see 3.5 GB rather than the whole 4GB that are availble. Any ideas on why this is happening and what can be done to resolve it will be appreciated.

guanx · 01-20-2011, 12:36 PM

Try either a PAE kernel or a x86_64 kernel.

Darth Vader · 01-20-2011, 12:38 PM

If you run Slackware (32 bits), those results are absolutely normal, because it use HIGHMEM4G.

If you want to use the whole memory, you should build (and use) a kernel using HIGHMEM64G, or use a x86_64 kernel, like our friend guanx said, or to switch entirely to Slackware64.

volkerdi · 01-20-2011, 01:11 PM

Do you perhaps have some system memory that is claimed by the video card?

X3J11 · 01-20-2011, 02:07 PM

This is normal behaviour. When using the standard addressing mode of 32-bit processors, the address space is limited to 4GB (2^32 bits). Within this the kernel maps your physical RAM as well as any other memory mappable devices (such as the framebuffer of your video adapter). Additional memory beyond what can fit within this 4GB range is ignored.

One can circumvent this by using a kernel with Physical Address Extension (PAE) support. Processes continue to see only the 4GB address space, but the kernel itself can use up to 64GB (2^36 bits), mapping different ranges for each process.

The option to set when building a PAE-enabled kernel is "Processor Type and Features -> High Memory Support -> 64GB". You should check that your processor is capable of using PAE. This feature will be listed as 'pae' in the flags line from /proc/cpuinfo.

You could also switch to Slackware64, as mentioned, which takes advantage of the 64-bit addressing mode of modern processors.

http://en.wikipedia.org/wiki/32-bit
http://en.wikipedia.org/wiki/64-bit
http://en.wikipedia.org/wiki/Protected_mode
http://en.wikipedia.org/wiki/Physical_Address_Extension

H_TeXMeX_H · 01-20-2011, 02:54 PM

Quote:

Originally Posted by volkerdi

Do you perhaps have some system memory that is claimed by the video card?

I would have to agree with this. Usually 3.7 GB = memory reserved by other programs and 3.3 GB = no PAE, just an observation. Also note that in RAM manufacturer terms 4 GB = 4 000 000 000 bytes, so that may also account for it. You may want to check /proc/iomem for reserved RAM.

guanx · 01-20-2011, 03:20 PM

This user http://lkml.indiana.edu/hypermail/li...04.3/3436.html is also having ~3550 MB RAM from a Intel T7700 / 4GB system. T7700 also happens to be the best CPU supported by the OP's Dell Latitude D630. I suspect that the other user is using a similar machine.

BTW, Main memory manufactures usually use 1024 instead of 1000 as 1k.

GazL · 01-20-2011, 03:47 PM

Quote:

Originally Posted by H_TeXMeX_H

Also note that in RAM manufacturer terms 4 GB = 4 000 000 000 bytes, so that may also account for it.

I know it's common for storage manufacturers to play that game with hard-disk capacities and so on, but I've never seen anyone use a Gigabyte of anything other than 2^30 bytes when referring to system memory (RAM).

I'm not sure about chip based storage systems such as ssd and usb-sticks though.

AlleyTrotter · 01-20-2011, 05:56 PM

my slackware64-13.1 system even when adding the memory reserved for video by the BIOS does not get anywhere near 2^30 * 4

So Slack 64 will not solve your problem
john

GazL · 01-20-2011, 06:20 PM

Quote:

Originally Posted by AlleyTrotter

my slackware64-13.1 system even when adding the memory reserved for video by the BIOS does not get anywhere near 2^30 * 4

So Slack 64 will not solve your problem
john

Code:

gazl@slack:~$ uname -a
Linux slack 2.6.35.10 #2 SMP Thu Jan 6 19:06:19 CST 2011 x86_64 Intel(R) Core(TM)2 Duo CPU     E7400  @ 2.80GHz GenuineIntel GNU/Linux
gazl@slack:~$ free -b
             total       used       free     shared    buffers     cached
Mem:    4149428224  428998656 3720429568          0   36601856  196907008
-/+ buffers/cache:  195489792 3953938432
Swap:            0          0          0
gazl@slack:~$ bc
bc 1.06.95
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'. 

(2^30 * 4 ) - 4149428224
145539072

That's only 138MB shy of the 4GB.

Richard Cranium · 01-20-2011, 11:43 PM

I'm pretty close to the full 4G myself:

Code:

# uname -a
Linux furd 2.6.33.4 #2 SMP Tue Sep 21 17:28:38 CDT 2010 x86_64 AMD Athlon(tm) II X4 635 Processor AuthenticAMD GNU/Linux

# free -b
             total       used       free     shared    buffers     cached
Mem:    4150456320 4099387392   51068928          0 2239926272  779100160
-/+ buffers/cache: 1080360960 3070095360
Swap:   2039848960    1572864 2038276096

brianL · 01-21-2011, 05:32 AM

Code:

bash-4.1$ uname -a
Linux SlackB 2.6.33.4 #2 SMP Tue Sep 21 17:28:38 CDT 2010 x86_64 AMD Athlon(tm) 64 X2 Dual Core Processor 5200+ AuthenticAMD GNU/Linux
bash-4.1$ free -b
             total       used       free     shared    buffers     cached
Mem:    3887067136 1187000320 2700066816          0   66924544  646656000
-/+ buffers/cache:  473419776 3413647360
Swap:   1044570112          0 1044570112

That's 4 GB RAM with 256 MB shared video memory.

l0rddarkf0rce · 01-21-2011, 07:36 AM

Quote:

Originally Posted by Darth Vader

If you run Slackware (32 bits), those results are absolutely normal, because it use HIGHMEM4G.

If you want to use the whole memory, you should build (and use) a kernel using HIGHMEM64G, or use a x86_64 kernel, like our friend guanx said, or to switch entirely to Slackware64.

As Darth Vader suggested enableing HIGHMEM64G and recompiling the kernel did the trick. Thanks Darth! I also could had tried Slack64, but I have toooooooo many 32-bit apps that may make it a pain in the rear to get running. If I recall correctly Alien Bob has instructions on how to create a hybrid 64/32 box, but for now that's more work than I have time for. At some point, when I can spare a few cycles, I guess I can give that a try, but for now I'm a happy Slacker.

Thanks to all!

AlleyTrotter · 01-21-2011, 07:43 AM

uname -a
Linux retired 2.6.37 #4 SMP Fri Jan 7 21:59:55 EST 2011 x86_64 AMD Athlon(tm) 64 X2 Dual Core Processor 5000+ AuthenticAMD GNU/Linux

free -b
total used free shared buffers cached
Mem: 4017254400 2767958016 1249296384 0 93769728 1806434304
-/+ buffers/cache: 867753984 3149500416
Swap: 4301783040 0 4301783040

free -m
total used free shared buffers cached
Mem: 3831 2639 1191 0 89 1722
-/+ buffers/cache: 827 3003
Swap: 4102 0 4102

bc 1.06.95
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
(2^30 * 4 ) - 4017254400
277712896

thats looks like 256M for video
never looked at free using -b bytes before
Everything does come very close to adding up
Thanks for the lesson

john

Slax-Dude · 01-21-2011, 08:26 AM

Quote:

Originally Posted by AlleyTrotter

my slackware64-13.1 system even when adding the memory reserved for video by the BIOS does not get anywhere near 2^30 * 4

So Slack 64 will not solve your problem
john

That's not true.

Code:

root@vm-server:~# uname -a
Linux vm-server 2.6.33.4 #3 SMP Wed May 12 23:13:09 CDT 2010 x86_64 AMD Phenom(tm) II X4 965 Processor AuthenticAMD GNU/Linux
root@vm-server:~# free -m
             total       used       free     shared    buffers     cached
Mem:          7952       6141       1811          0        231       4005
-/+ buffers/cache:       1904       6048
Swap:         3906          0       3905

EDIT: ooops, misread your post (sorry)