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Date: Wed, 10 Apr 2013 22:12:45 +0200
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Subject: Re: Multiple page size support on FreeBSD?
From: Sebastian Feld <sebastian.n.feld@gmail.com>
To: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
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Cc: freebsd-hackers@freebsd.org, Benjamin Kaduk <kaduk@mit.edu>
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On Wed, Apr 10, 2013 at 7:49 PM, Wojciech Puchar
<wojtek@wojtek.tensor.gdynia.pl> wrote:
>> How do your tests work?  Do you examine PTEs directly to check for
>> superpages
>> or are you relying on the vm.pmap.pde sysctls?
>
>
> the later.
>
> anyway - algorithm described on list - that heuristics detects consecutive
> page access doesn't really help the urgent case - RANDOM access to large
> amount of memory.
>
> sequential access will get minimal improvement.
>
> IMHO the only way that really make sens is to add options to madvise to give
> kernel information about usage.

Solaris has an API to control the usage for large pages, search for
MPSS - multiple page size support.
It consists of APIs in madvise, and /usr/bin/pagesize -a to list all
available page sizes, and other stuff. Since this has been established
since at least Solaris 9 (and 10) and is used by database and HPC
software, it might be a good starting point.