The reason we did not use 64 bits O.S. due to we still have some problem run 64 bit ORACLE on X86_64.

I have another question: since server we have is "SMP" how come it can show 32 GB RAM on application like "top" and "free"?

Thanks.

--- 09/3/30 (一)，John R Pierce pierce@hogranch.com 寫道：

寄件者: John R Pierce pierce@hogranch.com 主旨: Re: [CentOS] How to check server kernel support 32 Gb RAM (X86, 收件者: centos@centos.org 日期: 2009 3 30 一 下午 2:24

...

we have CENTOS 4.7 (X86) on DELL server, I already put

32 GB RAM on it.  I can use "top" or "free" to check memory and it did show 32 GB.

...

I check REDHAT site and found it say:

The "SMP" kernel supports a maximum of 16GB of main

memory. Systems with more than 16GB of main memory use the "Hugemem" kernel.

...

I use "uname -r" to check kernel and it show:

# uname -r 2.6.9-78.0.13.ELsmp

It did NOT show "Hugemem", does this server kernel

support 32 GB or not?  If NOT how can I change kernel to "hugeme"?

Dare we ask why this isn't a 64bit server?    using 32gb of memory on a processor architecture that can only directly address 4GB at a time is kind of brutal, unless this server is handling a rather large number of connection sessions at the same time.    For instance, a 32bit database server will have a max of about 2.5GB of shared memory usable.

to install the hugemem kernel,     yum install kernel-hugemem reboot, and test this by selecting it in the grub menu, then adjust /boot/grub.conf to suit.

read the release notes carefully on hugemem, its a very high overhead thing, as the kernel runs in a private memory space seperate from the applications, so all kernel<->user transfers are complex and slow. http://www.centos.org/docs/4/html/release-notes/as-x86/

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