Best way to use more that 4 gigs of memory ?

[Bob Bishop]

Hi,

On 4 Nov 2007, at 21:11, Pete French wrote:

> I have been doing some experiments with runnign 32 bit processed on
> and amd64 kernel over the last couple of days and am wondering what
> the general feel is for the best way to use over 4 gigs of memory.  
> As far
> as I can see I have 3 options:
>
> 1) amd64 kernel + 64 bit processes
> 2) amd64 kernel + 32 bit processes
> 3) i386 kernel with PAE and 32 bit processes
>
> I was initially thinking that option 1 was the best, but  
> benchmarking it
> the programs take 3 times longer to run that option 2! This  
> astounds me
> and I intend to investigate why, but given it is rue then that  
> rules it out
> as a viable solution for deploying stuff.

I had similar results, I surmise (without evidence) it's to do with  
cache usage.

> Which leaves either 32 bit processes on a 64 bit kernel or  
> alternatively
> running under PAE on a 32 bit kerenel. I don't know a lot about PAE  
> and
> was wondering if anyone had any advice either way as to which  
> wouldbe the most
> stable and/or best performing.

If your workload is CPU-intensive it probably doesn't matter; if it  
isn't, I'd do some more experiments.

> cheers,
>
> -pcf.



--
Bob Bishop          +44 (0)118 940 1243
rb at gid.co.uk fax +44 (0)118 940 1295