Re: XFS performance issues: O_DIRECT and Linux 2.6.6+

[Steve Lord <lord@xxxxxxx>]

James Foris wrote:
> Nathan Scott wrote:
>
> > Hi James,
> >
> > On Mon, Sep 13, 2004 at 11:56:33AM -0500, James Foris wrote:
> >
> > > More correctly, it happened between 2.6.5 and 2.6.5-bk1
> > >
> > > So..... something in the 2.6.5-bk1 patchset caused the change.
> > > Any suggestions where to begin looking (other than fs/direct_io.x) ?
> >
> >
> > http://kernel.org/pub/linux/kernel/v2.6/snapshots/old/patch-2.6.5-bk1.log
>
> Yup... a bunch more.
>
> "Major surgery against the pagecache, radix-tree and writeback code"
>
> The interesting question is; why do XFS and REISER suffer under O_DIRECT
> when other file systems improve?  And why does s/w RAID0 with an external
> journal suffer much worse than a simple file system with an internal 
> journal?
> Do these questions suggest anyplace else to look ?
Cache invalidation before and after O_DIRECT seems like a good starting
point. The raid0 external journal thing is probably a separate issue.

Steve