[Discuss] Limiting amount of memory

[Jerry Natowitz]

Linux kernel dynamically sizes a lot of buffers and other data 
structures depending on how much memory you have.  In some cases, like 
page maps, the size is dictated by the memory size.

If you do a free without the -g and/or save and compare dmesg (you may 
need to cut -c16 to remove time stamps) you will get an idea of how may 
tables are resized.

	Jerry Natowitz
===>    j.natowitz (at) gmail.com

On 09/12/13 16:50, Tim Callaghan wrote:
> I'm trying to reduce the amount of available memory on a Dell R710.  It has
> 48GB installed, I want to be able to boot it with 8G and 16G for some of my
> benchmarks.
>
> I've modified my /etc/grub.conf file, copying the top section and adding to
> the end of the kernel line as follows:
>
> kernel /boot/vmlinuz-2.6.18-348.3.1.el5 ro root=LABEL=/ mem=8G
>
>
> My problem is that with the "mem=8G" option, "free -g" reports 6G.  With
> mem=16G, "free -g" reports 9G.
>
> What am I missing?
>
> Thanks in advance,
>
> Tim
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