Linux-kernel mailing list archive 2000-23,: Re: New Linux 2.5 - 2.6 TODO (Alan Cox suggestsdelaying

# Re: New Linux 2.5 - 2.6 TODO (Alan Cox suggestsdelaying

Andi Kleen (ak@suse.de)
Tue, 6 Jun 2000 16:00:23 +0200

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On Tue, Jun 06, 2000 at 06:30:03AM -0700, Chris Mason wrote:
> We need two things:
>
> 1) a way to reserve and release a pinned page count. This will allow a
> pinned page high watermark so the journaled filesystems can plan nice
> without pinning all the ram.
>
> 2) A memory pressure call back in the address space operations. This
> really does seem more flexible than a call in struct super_operations.

This would involve that the pages in the transaction are added to the global
LRU (otherwise there would be no easy way to get at their transactions).
Does that really make sense ? I would guess that putting very different
things (normal write behind pages, write behind pages waiting for a
transaction and high priority log pages) into the same LRU does not
make sense.

I was more thinking about something like:

- Every journal maintains a pinned page counter per file system that is
linked into a global list (that could be the super block or a separate
structure). Using the address space operations for that seems to be overkill,
because there are many of them (you probably want one per journal/fs, not
one per inode)

- Try_to_free_pages walks this structure (probably with an similar algorithm
as the current swapper) and tells the journals to free some pages.

-Andi

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