Re: cache coloring

[Dario Faggioli <dario.faggioli@citrix.com>]

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On ven, 2013-11-22 at 10:48 +0100, Andrea Braschi wrote:
> Hi everybody,
>
Hello, and welcome!

> I'm Andrea and I'm a student from Politecnico di Milano, for a project
> at my university I need to implement cache coloring for the third
> level cache for xen-4.2.3 .
>
Ok, two questions:

1. My "OS concepts" my be a bit rusty, but I only remember something
   called page coloring. Both Google and Wikipedia seems to agree that
   page and cache coloring are the same thing, but then I don't
   understand why you specifically mention L3 above. Can you confirm
   that it is this that you are after?
   http://en.wikipedia.org/wiki/Cache_coloring
   http://www.freebsd.org/doc/en/articles/vm-design/page-coloring-optimizations.html

2. Why 4.2.3 and not upstream?

> -where is the code implementing the buddy allocator for the third
> level caches?(i've found two buddies but none of them seems to me the
> right one...I'll be implementig this in order to support x86 64 bit
> architecture)
> 
As far as I know (and as far as I'm able to grep :-)), I think you
should start looking at xen/common/page_alloc.c.

$ grep -i buddy xen/* -R
xen/arch/x86/x86_64/mm.c:     * buddy allocator relies on this assumption.
xen/arch/x86/x86_64/mm.c:     * Mark the allocated page before put free pages to buddy allocator
xen/common/page_alloc.c: * Simple buddy heap allocator for Xen.
xen/common/page_alloc.c: * BINARY BUDDY ALLOCATOR
xen/common/page_alloc.c:/* Remove any offlined page in the buddy pointed to by head. */
xen/common/page_alloc.c: * not freeing it to the buddy allocator.

> -there's a documentation about it?
> 
At this level, and for these kind of things, the code itself is the only
existent documentation. :-)

> I apologize if that's not the right list (if it's not please tell me
> where I can ask) and I hope I was clear in explaining my problem.
> 
It is the right place, so feel free o ask. The only thing that is
required is to be as specific as possible, i.e., describe your goal,
what it is that you are doing to achieve it and what it is that is not
working / you are not understanding.

This is a nice guide/checklist:
 http://wiki.xenproject.org/wiki/Asking_Xen_Devel_Questions

Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
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Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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