Re: Linux v.s. Mac OS-X Performance

Scott Marlowe wrote:
> On Nov 12, 2007 11:29 AM, Sam Mason <sam@samason.me.uk> wrote:
>> You don't need a 32bit kernel to support 8GB of memory should you? As
>> long as the kernel supports PAE that should be enough to make use of it.
>> You only need a 64bit address space when each process wants to see more
>> than ~3GB of RAM.
> 
> There's a performance hit for using PAE.  Not sure what it is, but I
> recall it being the in the 5 to 10% range.

Also, using PAE *used* to require the (OS-internal) use of 'bounce-buffers'
to copy data from processes high-up in memory down to i/o devices low-down
in memory.  I don't know if that's still an issue or not with 2.6 kernels,
but I could see it still being the case and, if so, seems like it would have
a significant impact on I/O bound tasks (like most DB processing...)


-- 
Steve Wampler -- swampler@noao.edu
The gods that smiled on your birth are now laughing out loud.