From: | Steve Wampler <swampler(at)noao(dot)edu> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Linux v.s. Mac OS-X Performance |
Date: | 2007-11-12 17:44:43 |
Message-ID: | 4738910B.2070603@noao.edu |
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Lists: | pgsql-general |
Scott Marlowe wrote:
> On Nov 12, 2007 11:29 AM, Sam Mason <sam(at)samason(dot)me(dot)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(at)noao(dot)edu
The gods that smiled on your birth are now laughing out loud.
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