1 02/28/85 vtoc_buffer_meters
 2 
 3 Syntax as a command:  vtoc_buffer_meters {-control_arg}
 4 
 5 
 6 Function:  provides information about the utilization of volume table
 7 of contents (VTOC) buffers.
 8 
 9 
10 Control arguments:
11 -report_reset, -rr
12    generates a full report and then performs the reset operation.
13 -reset, -rs
14    resets the metering interval for the invoking process so that the
15    interval begins at the last call with -reset specified.  If -reset
16    has never been given in a process, it is equivalent to having been
17    specified at system initialization time.
18 
19 
20 Access required:  This command requires access to phcs_ or
21 metering_gate_.
22 
23 
24 Notes:  If the vtoc_buffer_meters command is given with no control
25 argument, it prints a full report.
26 
27 The following are brief descriptions of the metering variables printed
28 out by the vtoc_buffer_meters command.
29 
30 The first section of the output (labeled "Routine") displays the number
31 of calls to VTOC buffer management routines.  In each of these, the
32 data is presented as number of calls and as average time between calls
33 (ATB).  The routines included are the following:
34 get_vtoce
35    called to read a VTOC entry, waiting for the I/O if the desired
36    VTOCE entry is not already in a VTOC buffer.
37 
38 
39 put_vtoce
40    called to write a VTOC entry without waiting for the I/O to
41    complete.
42 alloc_and_put_vtoce
43    called to obtain a free VTOC entry, read the VTOC entry, and write
44    it back to disk.
45 free_vtoce
46    called to return a VTOC entry to the free pool after nulling it and
47    writing the nulled entry to disk.
48 await_vtoce
49    called to await the completion of a VTOC write I/O generated by a
50    previous call (e.g., to put_vtoce).
51 
52 
53 GET_BUFFERS
54    an internal routine to obtain a VTOC buffer for a specified VTOC
55    entry.  It first checks whether a buffer is already assigned to the
56    VTOC entry (if so, this is considered a "Hit").  If a buffer is not
57    assigned, the routine selects one for the VTOC entry.
58 WAIT
59    an internal procedure to wait for completion of all I/Os for a given
60    VTOC buffer.  "TC Waits" are the number of times it was necessary to
61    relinquish the CPU to wait for I/O completion.
62 
63 
64 The next section of the output (labeled "Buffer Allocation") displays
65 data on the performance of the buffer selection algorithm (the routine
66 GET_BUFFERS).
67 Steps
68    is the number of times a buffer was examined by the selection
69    algorithm.
70 Skips
71    is the number of times a buffer was skipped by the selection
72    algorithm.  This is refined by the reason for the skip, as follows:
73 
74    os - an I/O was in progress for the buffer.
75 
76 
77    hot - the buffer contained a VTOC entry that could not be written to
78    disk because of irrecoverable write errors.
79 
80    wait - some process was waiting for completion of I/O activity to
81    this buffer.
82 
83 The last section of the output (labelled "Disk I/Os") lists the number
84 of disk reads and writes to the VTOC.