Re: [Lhms-devel] CONFIG_NONLINEAR for small systems

[Hirokazu Takahashi <taka@valinux.co.jp>]

Hello, Andy,

What version of kernel are you using?
I recommend linux-2.6.9-rc4-mm1 for your purpose, as it has eliminated
bitmaps for free pages to simplify managing buddy allocator.
This may help you.

> Following this email will be a series of patches which provide a
> sample implementation of a simplified CONFIG_NONLINEAR memory model. 
> The first two cleanup general infrastructure to minimise code 
> duplication.  The third introduces an allocator for the numa remap space 
> on i386.  The fourth generalises the page flags code to allow the reuse 
> of the NODEZONE bits.  The final three are the actual meat of the 
> implementation for both i386 and ppc64.
> 
> 050-bootmem-use-NODE_DATA
> 060-refactor-setup_memory-i386
> 080-alloc_remap-i386
> 100-cleanup-node-zone
> 150-nonlinear
> 160-nonlinear-i386
> 170-nonlinear-ppc64
> 
> As has been observed the CONFIG_DISCONTIGMEM implementation
> is inefficient space-wise where a system has a sparse intra-node memory
> configuration. For example we have systems where node 0 has a
> 1GB hole within it. Under CONFIG_DISCONTIGMEM this results in the
> struct page's for this area being allocated from ZONE_NORMAL and
> never used; this is particularly problematic on these 32bit systems
> as we are already under severe pressure in this zone.
> 
> The generalised CONFIG_NONLINEAR memory model described at OLS
> seemed provide more than enough decriptive power to address this
> issue but provided far more functionality that was required.
> Particularly it breaks the identity V=P+c to allow compression of
> the kernel address space, which is not required on these smaller systems.
> 
> This patch set is implemented as a proof-of-concept to show
> that a simplified CONFIG_NONLINEAR based implementation could provide
> sufficient flexibility to solve the problems for these systems.
> 
> In the longer term I'd like to see a single CONFIG_NONLINEAR
> implementation which allowed these various features to be stacked in
> combination as required.
> 
> Thoughts?
> 
> -apw
> 
> 
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