[Beowulf] partitioning L3 by page coloring

Brice Goglin brice.goglin at gmail.com
Mon Apr 8 13:17:09 PDT 2013


/proc/<pid>/pagemap can give you some information about physical pages
if I remember correctly.

Also, I wonder if huge pages could help enforcing the color. These pages
are contigous in physical memory and well aligned, so you know a lot
about the physical addresses in there. If cache coloring uses some of
those known bits, it may be possible to manually allocate with a
specific color within the huge page?

Brice





Le 08/04/2013 16:28, Rayson Ho a écrit :
> I don't think it can be done if you are not changing the kernel page
> allocator. Physical/virtual page mapping is all done by the kernel -
> in the end, page faults are transparent in the userspace.
>
> Even the traditional page coloring needs help from the kernel. There's
> the "Compiler-directed page coloring for multiprocessors" work done by
> Todd C. Mowry (another U of Toronto prof), but I don't recall seeing
> any pure userspace page coloring techniques - and I would imagine it
> is not entirely possible as the userspace doesn't know the physical
> page address.
>
> http://dl.acm.org/citation.cfm?id=237195
>
> Rayson
>
> ==================================================
> Open Grid Scheduler - The Official Open Source Grid Engine
> http://gridscheduler.sourceforge.net/
>
>
>
> On Mon, Apr 8, 2013 at 12:31 PM, Max R. Dechantsreiter
> <max at performancejones.com> wrote:
>> Rayson,
>>
>> ...In the paper you cited, I found the authors modified the
>> Linux kernel page allocator: that approach seems far beyond
>> what would be practical, or available to, a user not very
>> sophisticated regarding kernel issues.  (Also, this must be
>> hard to get correct!)
>>
>> I am not looking for the absolute best solution, if such
>> exists; just a "quick and dirty" scheme I could use to test
>> for benefit.
>>
>>
>> Regards,
>>
>> Max
>> ---
>>
>> On Mon, 8 Apr 2013, Rayson Ho wrote:
>>
>>> That technique was used in some of my U of Toronto friends' PhD thesis
>>> research & projects:
>>>
>>> "Managing Shared L2 Caches on Multicore Systems in Software"
>>>
>>> "Reducing the Harmful Effects of Last-Level Cache Polluters with an
>>> OS-Level, Software-Only Pollute Buffer"
>>>
>>> http://www.eecg.toronto.edu/~tamda/
>>>
>>> IIRC, all those techniques are OS only, with no changes to the CPU MMU
>>> or cache mapping logic.
>>>
>>> Rayson
>>>
>>> ==================================================
>>> Open Grid Scheduler - The Official Open Source Grid Engine
>>> http://gridscheduler.sourceforge.net/
>>>
>>>
>>>
>>> On Sat, Apr 6, 2013 at 1:54 PM, Max R. Dechantsreiter
>>> <max at performancejones.com> wrote:
>>>>
>>>> Would anyone with successful experience using this technique be willing
>>>> to share details, and warn of pitfalls?
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