kern/97686: massive NFS server performance break under "options QUOTA"

[Kris Kennaway]

The following reply was made to PR kern/97686; it has been noted by GNATS.

From: Kris Kennaway <kris at obsecurity.org>
To: "Ralf S. Engelschall" <rse at FreeBSD.org>
Cc: FreeBSD-gnats-submit at FreeBSD.org
Subject: Re: kern/97686: massive NFS server performance break under "options QUOTA"
Date: Thu, 25 May 2006 04:36:29 -0400

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 On Tue, May 23, 2006 at 01:58:20PM +0200, Ralf S. Engelschall wrote:
 
 >    After an upgrade we experienced massive serious NFS server problems
 >    on a NFS server under FreeBSD 6.1-STABLE (as of 2006-05-23). It
 >    still worked fine (exactly same kernel configuration) under FreeBSD
 >    5.4-STABLE (as of about December 2005).
 >   =20
 >    The effect is that the machine becomes totally unusable (nearly a
 >    system freeze) after about 10 minutes of just moderate NFS traffic
 >    of a single NFS client. We figured out that once the "options QUOTA"
 >    was removed from the kernel configuration the machine performance
 >    was 100% ok and we do not experience any performance breaks again.
 >    Even disabling SMP or deconfiguring all Netgraph configurations (for
 >    interface bundling and Netflow statistics) caused no effect. Only the
 >    "options QUOTA" caused the problem and its removal finally fixed the
 >    problem.
 >=20
 >    There seems to be a strange interaction between NFS and UFS Quotas...
 
 FYI, this might be due to the changes to vfs_lookup.c that I merged
 just before the release (originally by Jeff).  There are other reports
 of this problem on -stable@; I'm not clear if all of them involve
 quotas though.  As a temporary workaround you can revert that commit,
 although that's not a solution since that commit fixed other problems.
 
 Hopefully a solution will be found in the next week.
 
 Kris
 
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