Debian Bug#235886: nfs-kernel-server inducing load of 8-9 with no good reason for Linux 2.6 clients

[Chip Salzenberg <chip@pobox.com>]

Neil (or someone), what should I tell this user?


----- Forwarded message from "Steinar H. Gunderson" <sgunderson@bigfoot.com> -----

Subject: Bug#235886: nfs-kernel-server inducing load of 8-9 with no good reason for Linux 2.6 clients
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
To: Debian Bug Tracking System <submit@bugs.debian.org>
Date: Wed, 03 Mar 2004 00:41:21 +0100
X-Mailer: reportbug 1.50

Package: nfs-kernel-server
Version: 1:1.0-2woody1
Severity: important

It appears that from time to time, our NFS servers (both 2.4 and 2.6
servers, but both running woody) seem to go into giant loads with almost
no traffic (ie. 20-30 connections, but almost no file activity, as
confirmed by tcpdump). This is typically in the 7-8-9 range, and the
clients in question seem to hang almost indefinitely (like 20 minutes
for a simple ls). However, top shows no processes wanting CPU time, so
it almost looks like some kind of I/O starvation problem.

In addition, we seem to get strange errors like:

  00:16:32.330039 129.241.93.186 > 129.241.93.30: icmp: ip reassembly time exceeded [tos 0xc0] 

(.30 is the NFS server, .186 is one of the NFS clients)
  
Something is clearly wrong here; stopping nfs-kernel-server makes the
load drop to zero almost immediately, and substituting nfs-user-server for
nfs-kernel-server also fixes the problem. The servers in question are
also NFS clients, but there are no stale mounts and we aren't using NFS
re-export.

These problems seem to coincide with the rollout of Linux 2.6.x (seen
the problem with both 2.6.1 and 2.6.3) on the clients, so it seems
plausible that something in the Linux 2.6 client is triggering the NFS
kernel server code. I'm a bit unsure if I should file this on
nfs-kernel-server or on a kernel package; feel free to reassign as
needed.

-- System Information
Debian Release: 3.0
Architecture: i386
Kernel: Linux cassarossa 2.4.25 #1 SMP Wed Feb 18 22:46:21 CET 2004 i686
Locale: LANG=en_US, LC_CTYPE=en_US.ISO8859-1

Versions of packages nfs-kernel-server depends on:
ii  debconf                    1.2.35        Debian configuration management sy
ii  libc6                      2.2.5-11.5    GNU C Library: Shared libraries an
ii  libwrap0                   7.6-9         Wietse Venema's TCP wrappers libra
ii  nfs-common                 1:1.0-2woody1 NFS support files common to client

----- End forwarded message -----

-- 
Chip Salzenberg               - a.k.a. -               <chip@pobox.com>
"I wanted to play hopscotch with the impenetrable mystery of existence,
    but he stepped in a wormhole and had to go in early."  // MST3K


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