Fedora 10 / kernel PAE / 4GB RAM

[V13]

On Friday 03 April 2009, Lysimachos Zografos wrote:
> Απο οτι εχω κοιταξει στο net και σε
> λιστες ολοι το PAE προτεινουν ως λυση.
> Δεν γνωριζω καλυτερα. Θα το κοιταξω.

To PAE einai kati poy yparxei ston epeksergasi. To bigmem einai to onoma poy 
dinei to debian (kai alloi?) se kernels poy parolo poy einai i386 
yposthrizoyn >4GB mnimi me xrisi toy PAE.

Parolo poy mporei na eisai OK me to PAE kai ton kernel, kapoio meros ths 
mnimis mporei na min einai prospelasimo (AFAIK: ayto poy xrhsimopoieitai gia 
to PCI). Kata kanona tha prepei oxi mono na yposthrizei to PAE o 
epeksergastis kai na to xrisimopoiei o pyrinas, alla kai to BIOS na parei ena 
komati ths fysiki soy mnimis kai na to paroysiasei san na brisketai pano apo 
ta 4GB. Ayto kanei to "memory remap" h opos to leei o to kathe BIOS kai AFAIK 
xreiazetai eite exeis i386 eite exeis amd64. To poso ths mnimis poy den 
blepeis poikilei analoga me th periptosi.

Des ena aposspasma apo to /proc/iomem:

00100000-cff6ffff : System RAM ~= 3.2GB
...
d0000000-dfffffff : PCI Bus 0000:01 ~= 256MB (VGA)
...
100000000-12fffffff : System RAM ~= 0.8GB

(To mixanima exei 4GB mnimi kai trexei amd64 kernel. Xreiastike to remap.)

To teleytaio den tha ypirxe diathesimo an den ginotan to remaping mias kai h 
mnimi tha ypirxe sto eyros 0xcff6ffff-0x100000000 opoy pano ginetai to 
mapping ton PCI syskeyon (kai otidipote allo xreiastei).

Ayto poy den ksero einai ean to xreiazontai oloi oi kataskeyastes MB h mono h 
Asus kai an xreiazetai se ola ta montela h oxi. Isos kapoioi na to kanoyn 
by-default. Apo ayta poy exo dei, xreiazesai kai chipset poy na to 
yposthrizei. Nomizo oti to 945 den to yposthrizei eno to 965 to yposthrizei.

Oso kai na soy fainetai periergo pantos, isos na einai kalitera na min 
xrisimopoieis to PAE. Gia na doylepsei prosithetai ena akomi epipedo 
indirection sth prospelash ths mnimis (tria epipeda anti gia dyo) me 
antiktypo se arketa pragmata. Ayto symbainei eidika stis periptoseis opoy 
exeis polla context switches. Sto [2] leei oti symfona me th Redhat, to 
overhead einai ths taksis toy 1-10%.

<<V13>>

[1] http://en.wikipedia.org/wiki/Physical_Address_Extension
[2] http://www.held.org.il/blog/?p=79