[Q] kernel vs user memory (how to get more kernel mem)

[Q] kernel vs user memory (how to get more kernel mem)

[Till Immanuel Patzschke]

Hi,

another simple (?) question - sorry for asking.  There seems to be some
(fixed?) ratio user ./. kernel memory.  How do I change the amount of kernel
memory.  I got a reply telling the std ratio is 3:1 - where/how do I change it?
Thanks for the help,

Immanuel

--
Till Immanuel Patzschke                 mailto: tip@internetwork-ag.de
interNetwork AG                         Phone:  +49-(0)611-1731-121
Bierstadter Str. 7                      Fax:    +49-(0)611-1731-31
D-65189 Wiesbaden                       Web:    http://www.internetwork-ag.de

Re: [Q] kernel vs user memory (how to get more kernel mem)

[Eli Carter]

Till Immanuel Patzschke wrote:
> 
> Hi,
> 
> another simple (?) question - sorry for asking.  There seems to be some
> (fixed?) ratio user ./. kernel memory.  How do I change the amount of kernel
> memory.  I got a reply telling the std ratio is 3:1 - where/how do I change it?
> Thanks for the help,

Very carefully, and with architecture-specific concerns.
There are some #defines you will probably need to study:
PAGE_OFFSET
TASK_SIZE
and probably others...
in at least the ARM architecture, ioremap is also a concern with
VMALLOC_START and VMALLOC_END

Someone else may have a pat answer just to get the job done, though.

HTH,

Eli
--------------------.     Real Users find the one combination of bizarre
Eli Carter           \ input values that shuts down the system for days.
eli.carter(a)inet.com `-------------------------------------------------

Re: [Q] kernel vs user memory (how to get more kernel mem)

[Eric W. Biederman]

Till Immanuel Patzschke <tip@internetwork-ag.de> writes:

> Hi,
> 
> another simple (?) question - sorry for asking.  There seems to be some
> (fixed?) ratio user ./. kernel memory.  How do I change the amount of kernel
> memory.  I got a reply telling the std ratio is 3:1 - where/how do I change it?
> Thanks for the help,

Hmm.  There is a fixed ration of the amount of virtual address space
with each user space process having 3GB of virutal address space and
the kernel having 1GB.

But since the kernel implements paging the kernel can use all of the
RAM in the system.  While often times user space applications don't
haven't implemented the logic to use it all.

So for a good answer we need to know your application and why it is a
concern.

Eric