Re: Possible Idea with filesystem buffering.

Shawn Starr
2002-01-20T22:45:02Z

But why should each filesystem have to have a different method of
buffering/caching? that just doesn't fit the layered model of the kernel
IMHO.

Shawn.

On Sun, 20 Jan 2002, Hans Reiser wrote:

> In version 4 of reiserfs, our plan is to implement writepage such that
> it does not write the page but instead pressures the reiser4 cache and
> marks the page as recently accessed. This is Linus's preferred method
> of doing that.
>
> Personally, I think that makes writepage the wrong name for that
> function, but I must admit it gets the job done, and it leaves writepage
> as the right name for all filesystems that don't manage their own cache,
> which is most of them.
>
> Hans
>
> Shawn wrote:
>
> >I've noticed that XFS's filesystem has a separate pagebuf_daemon to handle
> >caching/buffering.
> >
> >Why not make a kernel page/caching daemon for other filesystems to use
> >(kpagebufd) so that each filesystem can use a kernel daemon interface to
> >handle buffering and caching.
> >
> >I found that XFS's buffering/caching significantly reduced I/O load on the
> >system (with riel's rmap11b + rml's preempt patches and Andre's IDE
> >patch).
> >
> >But I've not been able to acheive the same speed results with ReiserFS :-(
> >
> >Just as we have a filesystem (VFS) layer, why not have a buffering/caching
> >layer for the filesystems to use inconjunction with the VM?
> >
> There is hostility to this from one of the VM maintainers. He is
> concerned that separate caches were what they had before and they
> behaved badly. I think that they simply coded them wrong the time
> before. The time before, the pressure on the subcaches was uneven, with
> some caches only getting pressure if the other caches couldn't free
> anything, so of course it behaved badly.
>
> >
> >
> >Comments, suggestions, flames welcome ;)
> >
> >Shawn.
> >
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