[Info-vax] DNFS1ACP using 100% of CPU

[Sum1]

Hi All

I am using (still) a DS10L with 512Mb running OpenVMS v8.3 and TCP/IP 
as follows:

tcpip sho ver

  HP TCP/IP Services for OpenVMS Alpha Version V5.6
  on an AlphaServer DS10L 466 MHz running OpenVMS V8.3

NFS version info is:

Network File System:
  TCPIP$CFS_SHR;1            V5.6-9           22-JUN-2006  SYS$COMMON:[SYSLIB]
  TCPIP$DNFSACP;1            V5.6-9           22-JUN-2006  SYS$COMMON:[SYSEXE]
  TCPIP$DNFSDRIVER;1         V5.6-9           22-JUN-2006  SYS$COMMON:[SYS$LDR]
  TCPIP$DNFS_MOUNT_SHR;1     V5.6-9           22-JUN-2006  SYS$COMMON:[SYSLIB]
  TCPIP$LOCKD;1              V5.6-9           22-JUN-2006  SYS$COMMON:[SYSEXE]
  TCPIP$MOUNTD;1             V5.6-9           22-JUN-2006  SYS$COMMON:[SYSEXE]
  TCPIP$NFS_SERVER;1         V5.6-9           22-JUN-2006  SYS$COMMON:[SYSEXE]
  TCPIP$NFS_SERVICES;1       V5.6-9           22-JUN-2006  SYS$COMMON:[SYS$LDR]
  TCPIP$NFSSTAT;1            V5.6-9           22-JUN-2006  SYS$COMMON:[SYSEXE]
  TCPIP$PCNFSD;1             V5.6-9           22-JUN-2006  SYS$COMMON:[SYSEXE]
  TCPIP$STATD;1              V5.6-9           22-JUN-2006  SYS$COMMON:[SYSEXE]

NFS source (OSX) is mounted as follows:

TCPIP> sho mou/full
_DNFS1:[000000]	automount (inactivity timer    0 00:05:00.00), mounted
    OSX:/Volumes/stuff/data
    Transport                   TCPIP-UDP   Writing                     Enabled
    Read/write size             8192/8192   Write conversion            Enabled
    RPC timeout             0 00:00:01.00   ADF usage   NOUSE,NOUPDATE,NOCREATE
    RPC retry limit                     4   Fileids                      Unique
    Attribute time          0 00:00:15.00   Server type                    UNIX
    Directory time          0 00:00:30.00   Advisory Locking           Disabled
    Cache Validation          MODIFY TIME   Default user              [DEFAULT]
    Superuser                          No   Default UID,GID               -2,-2

The device is seen as:

sho dev/fu dnfs1

Disk DNFS1:, device type Foreign disk type 7, is online, mounted, file-oriented
    device, shareable, accessed via DFS or NFS.

    Error count                    0    Operations completed             814323
    Owner process                 ""    Owner UIC                      [SYSTEM]
    Owner process ID        00000000    Dev Prot    S:RWPL,O:RWPL,G:RWPL,W:RWPL
    Reference count                3    Default buffer size                 512
    Total blocks          2929605312    Sectors per track                     0
    Total cylinders                0    Tracks per cylinder                   0

    Volume label         "ALPHA$NFS"    Relative volume number                0
    Cluster size                   0    Transaction count                     3
    Free blocks              unknown    Maximum files allowed                 0
    Extend quantity                0    Mount count                           1
    Mount status              System    ACP process name             "DNFS1ACP"

  Volume Status:  ODS-5, access dates enabled.


Remote files are accessed by the server as an NFS client to an OSX 
server.  The configuration of both OSX and OpenVMS hasn't changed for a 
couple of years, with the exception of annual hobbyist license upgrades 
(and then a reboot) and six-monthly AUTOGENs.

In the last few days, DNFS1ACP has remained at 99% CPU and sometimes 
100% CPU for extended periods, bring the system to its knees and 
stopping almost all processing.  Running MONITOR SYSTEM shows this 
typical output:

> Node: NODE                 OpenVMS Monitor Utility      9-OCT-2013 12:46:03
> Statistic: CURRENT             SYSTEM STATISTICS
>                                                      Process States
>           ┌ CPU Busy (100)                                              
>                               ─┐         LEF:      18    LEFO:       0
>           │▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒│                                  
>     HIB:      18    HIBO:       0
> CPU     0 ├──────────────────────────┤ 100     COM:       5    COMO:       0
>           │▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒│         PFW:       0    CUR:        1
>           └──────────────────────────┘         MWAIT:     0    Other:      0
>           Cur Top: DNFS1ACP (100)                        Total: 42
> 
>           ┌ Page Fault Rate (48647) ─┐                                  
>                                                ┌ Free List Size (5941)  
>   ┐
>           │|▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒│                                  
>                       │▒▒                        │ 64K
> MEMORY  0 ├──────────────────────────┤ 500   0 ├──────────────────────────┤
>           │▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒│         │▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒          │ 16K
>           └──────────────────────────┘         └ Mod List Size (10699)    ┘
>           Cur Top: DNFS1ACP (48647)
> 
>           ┌ Direct I/O Rate (0)     ─┐                                  
>                                              ┌ Buffered I/O Rate (32)  
> ─┐
>           │                          │         │▒                       
>                                                         │
> I/O     0 ├──────────────────────────┤ 500   0 ├──────────────────────────┤ 500
>           │                          │         │▒                       
>                                                          │
>           └──────────────────────────┘                  
> └──────────────────────────┘
>           Cur Top:  (0)                        Cur Top: DNFS1ACP (20)

It stays in this state for about 30 seconds, then returns to normal, 
then back to 100%.

AUTOGEN doesn't recommend changing anything, there are no errors on the 
device or in OPERATOR.LOG.

Google hasn't provided any answers or even hints, looking for some 
suggestions of where to go next.  And if I have left out information 
that you consider vital to provide a reasonable answer, please let me 
know - I'm sure you will :)