Slow NFSv4 performance, was: Re: ZFSv28+NFSv4 poor file creation performance, "sync=disabled" has no effect

[Rick Macklem]

David Brodbeck wrote:
> On Mon, Sep 5, 2011 at 2:16 AM, Pawel Jakub Dawidek <pjd at freebsd.org>
> wrote:
> 
> > It would be good if you could try your test on FreeBSD directly.
> > This
> > way we could see if ZFS is to blame or NFS.
> >
> 
> Okay, it appears it is in fact an NFSv4 problem, and I've been barking
> up
> the wrong tree. I shared out an NFSv4 mountpoint with a UFS ramdisk as
> the
> backing store, and I got the same slow results. I was fooled by the
> fact
> that the numbers were similar to what I got using OpenSolaris with the
> ZIL
> enabled. (This is what I get for making assumptions.)
> 
> Interestingly enough, if I use NFSv3 instead of NFSv4, performance
> increases
> dramatically.
> 
Oops, it turned out that the 121 Opens for Fedora15 NFSv4 was because I
had delegations enabled on the server (which is not the default).

When I disabled that, I saw 61 Opens, just like the FreeBSD client and
as I would have expected.

So, the # of Opens is not the issue. Looking at the packet trace, I
did notice that the Open compound is rather complex. It includes the
following Ops:
PUTFH SAVEFH OPEN GETFH GETATTR RESTOREFH GETATTR
(most of these, except SAVEFH/RESTOREFH result in at least one VOP_xxx().)

But, I'm afraid that doesn't really help you.

Sorry, but no inspiration here, rick
ps: Please ignore the last post. It was mostly irrelevant, except that
    enabling delegations will make it even worse in this case.

> It appears it's FreeBSD's NFSv4 server, or the way it's interacting
> with
> Linux's client, that's the culprit here. I'm not sure if there are
> knobs I
> should be tweaking to make it perform better; any suggestions on what
> to try
> next?
> 
> --
> David Brodbeck
> System Administrator, Linguistics
> University of Washington
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