Need assistance to enable more that 4GB RAM on Linux 32Bit OS.

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Operating Systems Linux Need assistance to enable more that 4GB RAM on Linux 32Bit OS.
# 1  
Old 06-15-2010
Bug Need assistance to enable more that 4GB RAM on Linux 32Bit OS.

How to enable more than 4GB RAM support on Linux 32bit OS?

OS: CentOS release 5.4 (Final)
Kernel version: 2.6.18-53.el5
Arch: 32Bit

I got solution at • View topic - How to enable more than 4GB RAM support on Linux 32bit OS? but my question is the steps given there will work properly or not? Will new PAE kernel affect the server performance?

Need assistance from anybody....!


Last edited by Scott; 06-15-2010 at 11:42 AM.. Reason: Removed email and URL
# 2  
Old 06-15-2010
First and foremost is the question, does your system board actually support >4GB of RAM? Even many 64-bit boards don't, and if your system hardware doesn't you're out of luck no matter what kernel you use.

If your board does, and your processor supports PAE, go ahead and use the PAE kernel. There shouldn't be a performance hit so far as I can tell. PAE kernels won't boot on non-PAE processors, which is why it's packaged separately.
# 3  
Old 06-15-2010
Normally, addressing greater than normal bit capabilities comes with a performance penalty; albeit not a great one. Have you considered switching to a 64bit of the same OS?
# 4  
Old 06-15-2010
It's not really greater than normal bit capabilities... The processor supports it in hardware, and individual processes still run in a 32-bit address space, just mapped in from a larger pool of pages.
# 5  
Old 06-16-2010
Hello all, Thanks for your information and suggestions. Really appreciate your help.
# 6  
Old 06-16-2010
The performance impact is highly workload dependent, but on a fairly typical kernel compile,the PAE penalty works out to be around a 1% performance hit on RedHat’s test boxes.Testing with various other workload mixes has given performance
hits ranging from 0% to 10%.

From Redhat's 2.1 Virtual memory white paper. Things may have changed slightly in 2.6, but as such, it will still produce a slight performance hit.

Last edited by mark54g; 06-16-2010 at 10:52 PM..
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