Re: [NFS] NFS performance debugging

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Jun 25, 2008 at 09:02:42AM +0200, Adrian von Bidder wrote:
> On Tuesday 24 June 2008 22.29:31 J. Bruce Fields wrote:
> > On Tue, Jun 24, 2008 at 12:17:24PM +0200, Adrian von Bidder wrote:
> 
> > > Starting KDE, opening documents, sometimes also closing oo.org and
> > > saving documents takes several seconds longer than on local disk.
> >
> > "close" on nfs is an operation that requires a round-trip to the server
> > and waiting for the disk to commit any writes made before the close, so
> > if you've got to do a lot of those it can take time.  Fooling with the
> > journaling on the exported filesystem may help.
> 
> Are there tools to measure latencies on NFS?  Given a network dump, desired 
> output would be histograms of latencies by file operation?  (Or maybe I can 
> catch the information on the client, VFS side instead of NFS?
> 
> At this time, I really need to collect more data on where the problem is 
> since all I'm doing right now is fooling around based on assumptions... :-(
> 
> OTOH I'd suspect KDE/oo.org startup to be mostly reads of those config 
> files, so the problem shouldn't be close latencies.  Assumptions again.
> 
> > > TODO today: play around with NFSv4 on the shaky assumption that nfsv3
> > > is actually working but net latency is killing my performance.
> >
> > Delegations *might* help if the problem is really open latency.
> 
> First tries showed
>  * There are no acl on my files now

NFSv4 uses an entirely different type of ACL, for which you need
different client-side tools; see

	http://www.citi.umich.edu/projects/nfsv4/linux/nfs4-acl-tools/

>  * user id mapping seems funny: some users map to nobody, others map 
> correctly.  Huh?

And whereas v2/v3 require only uid's and gid's to agree, v4 (if you're
using auth_sys) requires uid's, gid's, *and* user and group names to
agree.

--b.

>  * Performance seems to be ok (timing desktop applications is always 
> difficult, and so far I'm working against on the production server with 
> varying load anyway...)
> 
> Haven't investigated these yet...


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