kernel memory map/usage/holes?

[Sonny Rao]

On Mon, Jul 17, 2006 at 02:06:57PM -0600, Chris Friesen wrote:
> 
> I've got a Maple board with 4GB of memory running a modified 2.6.10 
> kernel.  When it boots, I see the following in the logs:
> 
> 
> Top of RAM: 0x180000000, Total RAM: 0x100000000
> On node 0 totalpages: 1048576
>    DMA zone: 1048576 pages, LIFO batch:16
>    Normal zone: 0 pages, LIFO batch:1
>    HighMem zone: 0 pages, LIFO batch:1
> 
> 
> Then a bit later, I see:
> 
> 
> Memory: 4006976k/6291456k available (3408k kernel code, 2284124k 
> reserved, 1656k data, 448k bss, 220k init)
> 
> 
> 
> 1048576 pages works out to 4194304kB, so what happened to the 187328kB 
> that is the difference between the "Total RAM" and "Memory:" lines? 
> We've got an app that wants as much memory as possible, so I need to 
> explain where this 183MB of memory is being used.

I think it's part of the "reserved" category, which includes the MMU
hashtable.  I'd guess that's where it is.

Sonny