Re: [Qemu-devel] qemu & kernel :address generated are non-uniform

[Mulyadi Santosa <mulyadi.santosa@gmail.com>]

On Fri, Nov 18, 2011 at 21:49, sparsh mittal <sparsh0mittal@gmail.com> wrote:
> GBrange numberOfAddresses
>
> 0-0.5---> 3325
>
> 0.5-1---> 1253
>
> 1-1.5---> 0
>
> 1.5-2---> 30
>
> 2-2.5---> 0
>
> 2.5-3---> 1708
>
> 3-3.5---> 10521
>
> 3.5-4---> 0
>
> 4-4.5--> 15428

Hi...

I never observe the above address usage like you did, but I think that
is expected.

The reason is that Linux kernel tends to allocate from high memory
(above 896 MiB ) to allocate pages, including their page tables. This
is done to lower the "pressure" against normal memory zone.

Now for the "unbalance" case, I guess that's due the high usage of
slab. I am not sure where in fact they are started to be placed in
RAM. One thing for sure is that they act as cache for frequest used
objects such task structs, bio, socket buffers.

So, as you can take a guess. It's a mechanism in Linux memory
management which is quite complicated. Not sure if there's shortcut to
shape this up.

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com