mvfsstat

Synopsis

• Linux® and the UNIX® system:

mvfsstat [ –icrvVhalzAdF ] [ –o outfile] [ time ] [ count ]

• Windows®:

mvfsstat [ –iIcrvVhalzAdF ] [ –o outfile] [ time ] [ count ]

MVFS cache statistics

The –c option reports on the use of the host’s MVFS caches. This report is cumulative, covering the entire period since the MVFS was started. The following sections describe the particular statistics that are useful in tuning MVFS performance on a Rational® ClearCase® client host.

Directory name lookup cache (dnlc). The dnlc section reports on use of a name-lookup cache that maps pathnames to Rational ClearCase identifiers. Note that the value precedes the keyword. For example, 1301984 dot means that the reported value of the dot statistic is 1301984.

Cache hits. The hit line reports on the number of times an entry type was found in the cache (hit):

dot

Number of times the current working directory was looked up (always a cache hit)

dir

Number of times a directory object entry was found in the cache

reg

Number of times a file object entry was found in the cache

noent

Number of times a cached File not found (ENOENT) entry was found

This cache has low hit rates (around 50%) for activities that walk a large tree, for example, a find command, or a recursive clearmake that examines many files and determines that nothing needs to be built.

Cache misses. The miss line reports on total cache misses. The events value is the number of cache misses that occurred because of a significant VOB event, a time-out of the entry, or vnode recycling. Cache misses can occur because there was no entry in the cache. The total number of cache misses equals the events value plus the number of misses occurring because there was no entry in the cache.

Cache additions. The add line reports on cache misses that occurred because a new entry was being added to the cache. The additions are categorized as directory entries (dir), file entries (reg), and ENOENT entries (noent).

Attribute cache. The attr section reports on use of a cache of stat returns (Linux and the UNIX system) or object status inquiry records (Windows). This cache generally has hit rates comparable to those for the directory name lookup cache.

Options and arguments

time

Time in seconds between samples. Display deltas on each sample. If you omit this option, only the absolute values of all information are printed.

count

Number of samples. If omitted, defaults to "infinite".

–o outfile

Writes the output to outfile.

–i

Displays cleartext I/O counts and wait times.

–I

Displays count and wait times for Windows I/O Request Packets that the MVFS has processed.

–c

Displays statistics for the MVFS caches (see MVFS cache statistics).

–r

Displays MVFS remote procedure call (RPC) statistics. These statistics include both counts and real-time waited. Real-time waited may be greater than 100% of a sample period in two cases:

• When an operation takes longer to complete than the sample period; for example, 60 seconds of wait time is recorded in a 30-second sample.
• Multiple processes are waiting at the same time.

In general, real-time percentages are meaningful only when a single process is accessing a VOB.

–v

Displays counts of vnode operations.

–V

Displays counts of vfs operations.

–h

Displays an RPC histogram. Cleartext fetch RPCs are tallied separately from all other RPCs.

–a

Displays auditing statistics.

–l

Adds more detail to the statistics generated by –c, –r, –i, –I, –v, or –V, by providing a breakdown by individual operations. With –c, also provides per-cache-entry hit ratios.

–z

(Requires privileged user status.) Resets all running counters to zero.

–A

Displays all statistics.

–d

With –c or –A, displays additional debugging information for use in diagnosing problems. Use this option only under direction from IBM Software Support for Rational products.

–F

Displays statistics for mnode operations and the directory name lookup cache. Use this option only under direction from IBM Software Support for Rational products.