The following are demonstrations of the rfileio.d script.


rfileio.d prints file system statistics by file,

   # ./rfileio.d
   
   Read IOPS, top 20 (count)
   /lib/ld.so.1                                              logical          2
   /devices/pseudo/clone@0:ptm                               logical          4
   /usr/bin/grep                                             logical          4
   /devices/pseudo/pts@0:3                                   logical          4
   /extra1/contents                                         physical       1700
   /extra1/contents                                          logical      11582
   
   Read Bandwidth, top 20 (bytes)
   /devices/pseudo/pts@0:3                                   logical          3
   /devices/pseudo/clone@0:ptm                               logical         92
   /lib/ld.so.1                                              logical        212
   /usr/bin/grep                                             logical        269
   /extra1/contents                                         physical   48115712
   /extra1/contents                                          logical   94865162
   
   Total File System miss-rate: 50%
   ^C

   $ ls -l /extra1/contents
   -rw-r--r--   1 root     root     94865162 Nov  2 21:08 /extra1/contents

The /extra1/contents file was read using the grep command. The output shows
that half of the contents was returned from the cache, the other half from disk
(50% miss-rate). It is 94,865,162 bytes in size, which can be seen both in
the ls -l output and the logical read() bytes reported by rfileio.d. There
were 11,582 logical read() calls, which the disk driver satisfied by using
1,700 disk events (aggregation).



The following demonstrates many files being read. 

   # ./rfileio.d
   
   Read IOPS, top 20 (count)
   /usr/bin/amd64/glib-mkenums                               logical          4
   /usr/bin/amd64/glib-genmarshal                           physical          4
   /usr/bin/amd64/gdk-pixbuf-query-loaders                   logical          4
   /usr/bin/amd64/ls                                         logical          5
   /usr/bin/amd64/pargs                                      logical          5
   /usr/bin/amd64/ps                                         logical          5
   /usr/bin/amd64/gconf-merge-tree                          physical          6
   /usr/bin/amd64/cputrack                                   logical          6
   /usr/bin/amd64/gconftool-2                               physical          6
   /usr/bin/amd64/prctl                                      logical          6
   /usr/bin/amd64/prstat                                     logical          6
   /usr/bin/amd64/glib-genmarshal                            logical          7
   /usr/bin/amd64/truss                                     physical          8
   /usr/bin/amd64/sort                                       logical          9
   /usr/bin/amd64/prex                                       logical         10
   /usr/bin/amd64/gconf-merge-tree                           logical         13
   /usr/bin/amd64/mdb                                       physical         15
   /usr/bin/amd64/gconftool-2                                logical         15
   /usr/bin/amd64/truss                                      logical         26
   /usr/bin/amd64/mdb                                        logical         63
   
   Read Bandwidth, top 20 (bytes)
   /usr/bin/amd64/prctl                                      logical      36784
   /usr/bin/amd64/prctl                                     physical      36864
   /usr/bin/amd64/prstat                                     logical      44760
   /usr/bin/amd64/prstat                                    physical      45056
   /usr/bin/amd64/glib-genmarshal                            logical      46064
   /usr/bin/amd64/glib-genmarshal                           physical      46080
   /usr/bin/amd64/cputrack                                   logical      46912
   /usr/bin/amd64/cputrack                                  physical      47104
   /usr/bin/amd64/sort                                       logical      65120
   /usr/bin/amd64/sort                                      physical      65536
   /usr/bin/amd64/prex                                       logical      80968
   /usr/bin/amd64/prex                                      physical      81920
   /usr/bin/amd64/gconf-merge-tree                           logical     113592
   /usr/bin/amd64/gconf-merge-tree                          physical     122880
   /usr/bin/amd64/gconftool-2                                logical     129208
   /usr/bin/amd64/gconftool-2                               physical     139264
   /usr/bin/amd64/truss                                      logical     246360
   /usr/bin/amd64/truss                                     physical     262144
   /usr/bin/amd64/mdb                                        logical     627456
   /usr/bin/amd64/mdb                                       physical     638976
   
   Total File System miss-rate: 81%
   ^C

The miss-rate was 81%, meaning we are returning around 20% of the data from
the cache. Details for the top 20 files read by-bytes and by-count are listed;
this shows the /usr/bin/amd64/mdb file was read() 63 times, causing 15 disk
reads, and while 627,456 bytes were requested, 638,976 bytes were read from 
disk (the extra bytes are due to read-ahead and file system metadata).