After yesterdays post regarding the BIOS doesn't leave a aperture memory hole
issue, I got a very logical question that I forgot to ask myself as I was too happy to see the error message go away.
Quirinius said:
But did that boot option actually give you more memory? Did you check with "free -m"?
So I did a little bit of testing. Here is the output of the free command before the using boot-options on the CentOS machine.
total used free shared buffers cached
Mem: 4048440 804072 3244368 0 34324 428640
-/+ buffers/cache: 341108 3707332
Swap: 4200988 0 4200988
total used free shared buffers cached
Mem: 3953 785 3168 0 33 418
-/+ buffers/cache: 333 3620
Swap: 4102 0 4102
and here is after :
total used free shared buffers cached
Mem: 4048024 553232 3494792 0 30792 336400
-/+ buffers/cache: 186040 3861984
Swap: 4200988 0 4200988
total used free shared buffers cached
Mem: 3953 536 3416 0 30 328
-/+ buffers/cache: 177 3775
Swap: 4102 0 4102
I have also checked what is happening on my notebook which also has 4GB of RAM memory but unlike the rest of my machines does not have an AMD processor or an Asus Motherboard with Phoenix BIOS and here is what free had to say.
total used free shared buffers cached
Mem: 4059392 652816 3406576 0 13048 206600
-/+ buffers/cache: 433168 3626224
Swap: 2096472 0 2096472
total used free shared buffers cached
Mem: 3964 637 3326 0 12 201
-/+ buffers/cache: 423 3541
Swap: 2047 0 2047
Doing a little bit of math shows that ...
[thanassis@lxbakalidis ~]$ expr 4048024 - 4048440
-416
After the boot option is set our memory decreases by 416 bytes and the memory reported by Fedora on a system that does not display the IOMMU error message at all is
[thanassis@lxbakalidis ~]$ expr 4059392 - 4048440
10952
... bytes bigger. Now I understand that I am comparing results from two different kernel versions, so I performed the same test at home on my AMD/Asus based Fedora box and here are my results..
[thanassis@plouton ~]$ cat fedora-home-before.txt
total used free shared buffers cached
Mem: 4062232 490440 3571792 0 13816 177132
-/+ buffers/cache: 299492 3762740
Swap: 0 0 0
total used free shared buffers cached
Mem: 3967 479 3488 0 13 172
-/+ buffers/cache: 292 3674
Swap: 0 0 0
[thanassis@plouton ~]$ cat fedora-home-after.txt
total used free shared buffers cached
Mem: 4061820 1083232 2978588 0 34960 393808
-/+ buffers/cache: 654464 3407356
Swap: 0 0 0
total used free shared buffers cached
Mem: 3966 1055 2910 0 34 384
-/+ buffers/cache: 636 3329
Swap: 0 0 0
[thanassis@plouton ~]$ expr 4061820 - 4062232
-412
[thanassis@plouton ~]$
Addendum
This is only a closing statement to admit that I managed nothing. I tried changing my graphics adapter with a new NVIDIA using the new kernel updates and my CentOS machine just froze again.
So I switched everything back, got my 416 bytes back and try to keep an eye on the net and the forums in case I somehow find something to help me this.... :-(
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