Re: NFS client latencies

[Lee Revell]

On Wed, 2005-03-30 at 16:14 -0500, Trond Myklebust wrote:
> on den 30.03.2005 Klokka 11:56 (-0800) skreiv Andrew Morton:
> > > That's normal and cannot be avoided: when writing, we have to look for
> > > the existence of old nfs_page requests. The reason is that if one does
> > > exist, we must either coalesce our new dirty area into it or if we
> > > can't, we must flush the old request out to the server.
> > 
> > One could use the radix-tree tagging stuff so that the gang lookup only
> > looks up pages which are !NFS_WBACK_BUSY.
> 
> Yes. Together with the radix tree-based sorting of dirty requests,
> that's pretty much what I've spent most of today doing. Lee, could you
> see how the attached combined patch changes your latency numbers?
> 

Different code path, and the latency is worse.  See the attached ~7ms
trace.

Lee

Attachment: nfs-6776usec-trace.bz2
Description: application/bzip