[SunHELP] RAM usage

[gonufer]

John Kennedy wrote:
 > We have a user who is running a job on a Blade100 (Solaris8 1/01).
 > The job they are running requires as much of the 8gig of RAM as it
 > can get.  For some reason RAM usage stops at 4gig causing the job
 > to die.  How can we allow the job to use all 8gig

I guess the most important question is: is it a 64-bit application?
(run "file" on it).

A 32-bit application has a 32-bit address space which can only address
2^32 bytes of ram (4GB) but due to the current implementation of SunOS
a tiny bit of the address space is reserved at the top so the limit
is really closer to 3.99GB (it used to be 3.75GB until SunOS 5.7).

A 64-bit application can address 2^64 bytes of memory (16777216 TB) but
UltraSPARC I and UltraSPARC II processors (and derivative like that 
found in the Sun Blade 100) only have a 44-bit (virtual) MMU so each 
process' address space is really limited to 16TB (virtual).  The
UltraSPARC III is the first UltraSPARC to have a full 64-bit (virtual)
MMU.

-greg


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