1 The following are examples of seeksize.d.
3 seeksize.d records disk head seek size for each operation by process.
4 This allows up to identify processes that are causing "random" disk
5 access and those causing "sequential" disk access.
7 It is desirable for processes to be accesing the disks in large
8 sequential operations. By using seeksize.d and bitesize.d we can
9 identify this behaviour.
13 In this example we read through a large file by copying it to a
14 remote server. Most of the seek sizes are zero, indicating sequential
15 access - and we would expect good performance from the disks
16 under these conditions,
19 Tracing... Hit Ctrl-C to end.
22 22349 scp /dl/sol-10-b63-x86-v1.iso mars:\0
24 value ------------- Distribution ------------- count
26 0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 726
47 In this example we run find. The disk operations are fairly scattered,
48 as illustrated below by the volume of non sequential reads,
51 Tracing... Hit Ctrl-C to end.
54 22399 find /var/sadm/pkg/\0
56 value ------------- Distribution ------------- count
82 I found the following interesting. This time I gzipp'd the large file.
83 While zipping, the process is reading from one location and writing
84 to another. One might expect that as the program toggles between
85 reading from one location and writing to another, that often the
86 distance would be the same (depending on where UFS puts the new file),
89 Tracing... Hit Ctrl-C to end.
92 22368 gzip sol-10-b63-x86-v1.iso\0
94 value ------------- Distribution ------------- count
120 8388608 |@@@@@@@@@@@@@@@@@@ 536
126 The following example compares the operation of "find" with "tar".
127 Both are reading from the same location, and we would expect that
128 both programs would generally need to do the same number of seeks
129 to navigate the direttory tree (depending on caching); and tar
130 causing extra operations as it reads the file contents as well,
133 Tracing... Hit Ctrl-C to end.
139 value ------------- Distribution ------------- count
141 0 |@@@@@@@@@@@@@@@@@@@@ 251
167 22282 tar cf /dev/null /etc\0
169 value ------------- Distribution ------------- count