CentOS

Hi all,

I am trying to install kernel-pae in centos 6.9 server which has more than 4 GB RAM.
[root@localhost ~]# yum install kernel-pae
Loaded plugins: fastestmirror, refresh-packagekit, security
Setting up Install Process
Loading mirror speeds from cached hostfile
* base: mirror.vbctv.in
* extras: mirror.vbctv.in
* updates: mirror.vbctv.in
No package kernel-pae available.
Error: Nothing to do
[root@localhost ~]#

What is the procedure to enable physical address extension on CentOS 6.9?
Please let me know if there are any inputs.

Thanks

There is no separate PAE kernel in CentOS 6. Which kernel are you currently using? Please run uname -a (hostname can be edited out) and free -h.

[root@localhost ~]# uname -a
Linux localhost.localdomain 2.6.32-696.el6.i686 #1 SMP Tue Mar 21 18:53:30 UTC 2017 i686 i686 i386 GNU/Linux
[root@localhost ~]# free -h
total used free shared buffers cached
Mem: 5G 2G 3G 264K 228M 427M
-/+ buffers/cache: 1G 4G
Swap: 7G 0B 7G

Hi ,

I just wanted to know whether all applications running on PAE enabled kernel runs in PAE mode or
Application developer needs to specify it,like during compilation ,we need to include something which
will inform kernel to run this application in PAE mode.

Thanks in advance.

If I remember correctly, there is no separate PAE enabled 32 bit kernel for CentOS 6 because it's enabled by default - i.e all 32 bit el6 kernels are already PAE enabled.

Confirmed: https://access.redhat.com/solutions/425013

Also you really need to do a yum update, that kernel is very old and has a lot of security problems.

OK, so your kernel can see the RAM because "free" shows 5G as the total amount.

However, bear in mind that the programs you run are still 32bit and can access only up to 4GB per process (or somewhat less, depending on some details). You can't "enable" PAE mode for applications, it's a kernel level feature. This means you can't allocate a 8GB buffer in mysql, for example, even with PAE. PAE is still useful for some tasks, like if you have two processes each consuming 2.5GB, the kernel can use the full amount of RAM to accommodate both of those.

x86_64 is so much easier in this regard. I would recommend moving to 64bit if at all possible.

Thanks for all the inputs.