On Sun, Sep 23, 2001 at 03:40:33AM -0700, Matt Dillon wrote:
>
> :> VM Page Cache, and thus not be candidates for reuse anyway. So my patch
> :> has a very similar effect but without the overhead.
> :
> :Back when I rewrote the VFS namecache back in 1997 I added that
> :clause because I saw directories getting nuked in no time because
> :there were no pages holding on to them (device nodes were even worse!)
> :
> :So refresh my memory here, does directories get pages cached in VM if
> :you have vfs.vmiodirenable=0 ?
> :
> :What about !UFS filesystems ? Do they show a performance difference ?
> :
> :Also, don't forget that if the VM system gave preferential caching to
> :directory pages, we wouldn't need the VFS-cache very much in the first
> :place...
> :
> :--
> :Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
>
> Ah yes, vmiodirenable. We should just turn it on by default now. I've
Has the problem of small-memory machines (< 64M IIRC) solved now? As I
understand it vmiodirenable is counter-productive for these boxes.
Maybe one could decide on-boot whether the amount of mem is enough to
make it useful?
Just a thought of course.
> been waffling too long on that. With it off the buffer cache will
> remember at most vfs.maxmallocspace worth of directory data (read: not
> very much), and without VMIO backing, which means vnodes could be
> reclaimed immediately. Ah! Now I see why that clause was put
> in... but it's obsolete now if vmiodirenable is turned on, and it
> doesn't scale well to large-memory machines if it is left in.
--
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