01-21-2011
Performance problem - waiting on cache
My server is running HP-UX 11.23 and one Oracle database. The server has 8 CPUs and is mostly idle all the time. Buffer cache is set to 10%min/max with 5GB memory on the server.
I have a user complaining that a batch process is all of a sudden taking a long time to finish. The DBA gave me the PID of the offending query and when I look up that process in Glance it shows the reason for waiting is CACHE. I set the update interval to 1 second and it never changes from cache. The process is consuming little CPU but still waits on cache.
Eventually the process will finish and die but it takes much, much longer than it used to just a few days ago. I know of no other processes that exhibit this behavior yet everyday this one process does the same thing, even with a new PID.
My hypothesis is that the server thinks that some data resides in cache but does not so it waits and waits. This doesn't really make sense to me but I cannot think of anything else that might cause this.
I have tried scouring the net for answers and have found none. If someone has any kind of logical guess of what might cause this behavior I'd love to hear it. It might help me figure out what is really going on.
Thanks,
Kevin
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NFSSTAT(1) BSD General Commands Manual NFSSTAT(1)
NAME
nfsstat -- display NFS statistics
SYNOPSIS
nfsstat [-cseuv] [-w wait] [-n net|user] [-m [mountpath]]
DESCRIPTION
nfsstat displays statistics kept about NFS client and server activity, active user activity, exported directories, and mount information. In
the absence of any options, nfsstat displays NFS client and server statistics.
The options are as follows:
-c Show NFS client statistics.
-e Show NFS server exported directory statistics.
-m [mountpath]
Show NFS mount information.
-s Show NFS server statistics.
-u Show NFS server active user statistics.
-w wait
Display a shorter summary at wait second intervals.
-n net|user
Show network addresses as numbers, or show users as uid numbers. This option can appear multiple times.
-v Show additional information (if available).
OUTPUT
The data fields that nfsstat displays for each set of statistics are:
Client Information:
Statistics for NFS file system mounts.
RPC Counts
Counts of the RPC calls made to each of the NFS protocol procedures.
RPC Info
Statistics for NFS RPC calls:
TimedOut
RPC calls that timed out, perhaps to a slow or dead server.
Invalid
Invalid RPC replies.
X Replies
RPC replies received that did not have calls pending.
Retries
RPC calls that were retried.
Requests
Total number of RPC calls made.
Cache Info
Statistics on NFS client-side cache performance:
Attr Hits/Misses
Performance of the NFS file attribute cache.
Lkup Hits/Misses
Performance of the directory name lookup cache.
BioR Hits/Misses
Performance of block cache for reads.
BioW Hits/Misses
Performance of block cache for writes.
BioRL Hits/Misses
Performance of symbolic link cache.
BioD Hits/Misses
Performance of directory cache.
DirE Hits/Misses
Performance of directory offset cache.
Server Information:
Statistics for the NFS server.
RPC Counts
Counts of RPC calls on each of the NFS server's procedures are recorded here.
Server Ret-Failed
RPC errors returned by the server.
Server Faults
Errors in the NFS server.
Server Cache Stats
Statistics from the NFS server's RPC duplicate request cache:
Inprog
Calls already in progress.
Idem
Cache hits for idempotent procedures.
Non-idem
Cache hits for non-idempotent procedures.
Misses
Cache Misses.
Server Write Gathering
These statistics describe the efficiency of the NFS server's write gathering feature.
WriteOps
Write operations to disk.
WriteRPC
Write operations received by the server.
Opsaved
Write operations that were gathered (WriteRPC - WriteOps)
NFS Server Exported Directory Information:
Statistics for each exported directory on the NFS server.
NFS Requests
Count of NFS requests processed by an exported directory.
Bytes Read
Count of bytes read from an exported directory.
Bytes Written
Count of bytes written to an exported directory.
NFS Server Active User Information:
List of active NFS users and statistics on the NFS server.
NFS Requests
Count of NFS requests received from an active user.
Bytes Read
Count of bytes read by an active user.
Bytes Written
Count of bytes written by an active user.
Idle
Amount of time an active user has been idle.
User
Name (or uid if -n user was given) of active user.
IP Address
Host name (or network address if -n net was given) of client machine.
NFS Mount Information:
Information about the given NFS mount (or all NFS mounts).
The path mounted on and the server:/path that is mounted.
Mount arguments originally passed in to the mount.
Current mount parameter values and status information.
SEE ALSO
netstat(1), iostat(8), mount_nfs(8), nfsd(8)
HISTORY
The nfsstat command appears in 4.4BSD.
4.4BSD January 11, 2011 4.4BSD