On Wed, Mar 08, 2006 at 02:14:25AM +0100, Roland Mainz wrote:
> BTW: The discussion was about a _tuneable_ which could be set to a value
> used as default page size (used by kernel and returned by
> |getpagesize()|&co.) - the default for this tuneable should remain 8k.
> It would allow people to switch to 64k pages on demand and even allows
> them to return to the 8k size if something breaks (e.g. setting the
> tunable is not mandatory). Additionally a shared library similar to
> /usr/lib/[EMAIL PROTECTED] could be provided to switch to the old page size if
> individual userland applications cause trouble. And there would be a way
> to fix all those broken applications out there. Without having such a
> tuneable it is almost impossible to fix the applications which makes the
> situation even worse (which may backfire at some point in the future).
The problem here is that you lose most of the benefits in the kernel if the
size is tunable, in one of two directions:
either you still have 8k pages in the kernel (i.e. you have
4x the number of page_ts than you need, and you're *always* dealing
with large pages), or
you have to do complicated 64k-page-to-8k-page emulation logic for
those "legacy" apps.
In the end, the increase in complexity outweighed the benefits, and the
project was put aside. (I wasn't on the project, but I did have some
interactions with the project team)
Cheers,
- jonathan
--
Jonathan Adams, Solaris Kernel Development
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