[ltp] X60s 4 GB RAM PAE only 3 recognized (64 Bit)

Carl-Daniel Hailfinger linux-thinkpad@linux-thinkpad.org
Mon, 24 Nov 2014 15:36:06 +0100

Hi Richard,

On 23.11.2014 20:15, Richard Neill wrote:
> On 23/11/14 18:40, Carl-Daniel Hailfinger wrote:
>>> The X60s is a variant of the X60, which in turn is based on the same
>>> chipset as the T60 Thinkpad generation. The chipset used in this
>>> Thinkpad generation is only capable of addressing a maximum of 3GB RA=
> ... etc
> Thanks, that's really interesting to understand.
> Just wondering, does this also impose a limit on the maximum amount of
> RAM allocated to a process (or perhaps all processes) of 3.x GB, even
> on 64-bit? In particular, is it helpful to allocate 8GB of SSD as swap?=

The per-process virtual address space limit of 64 bit processes using a
64 bit kernel on a 64 bit CPU is large enough to not pose any paractical
barrier regardless of the chipset limitations present in the T60/X60.
That said, you may run out of room for page tables in kernel memory, so
more than 32 GB swap are not going to be practical. Besides that,
consider the crappy speed of the T60/x60 builtin SATA I interface before
you think of adding too much swap. The only IMO practical way to get
decent SATA speeds is to replace the WLAN miniPCIe card with a SATA
miniPCIe card, but then you'd have to use some USB WLAN adapter. Not
optimal, but doable.