Documentation/admin-guide/iostats.rst

56 or long-lived system; so applications should be prepared to deal with
58 int (32 bit) or unsigned long (32-bit or 64-bit, depending on your
59 machine) as noted per-field below. Unless your observations are very
63 system-wide stats you'll have to find all the devices and sum them all up.
65 Field  1 -- # of reads completed (unsigned long)
68 Field  2 -- # of reads merged, field 6 -- # of writes merged (unsigned long)
69     Reads and writes which are adjacent to each other may be merged for
74 Field  3 -- # of sectors read (unsigned long)
77 Field  4 -- # of milliseconds spent reading (unsigned int)
81 Field  5 -- # of writes completed (unsigned long)
84 Field  6 -- # of writes merged  (unsigned long)
87 Field  7 -- # of sectors written (unsigned long)
90 Field  8 -- # of milliseconds spent writing (unsigned int)
94 Field  9 -- # of I/Os currently in progress (unsigned int)
98 Field 10 -- # of milliseconds spent doing I/Os (unsigned int)
105 Field 11 -- weighted # of milliseconds spent doing I/Os (unsigned int)
112 Field 12 -- # of discards completed (unsigned long)
115 Field 13 -- # of discards merged (unsigned long)
118 Field 14 -- # of sectors discarded (unsigned long)
121 Field 15 -- # of milliseconds spent discarding (unsigned int)
125 Field 16 -- # of flush requests completed
131 Field 17 -- # of milliseconds spent flushing
141 almost a non-issue.  When the statistics are read, the per-CPU counters
144 user interface for accessing the per-CPU counters themselves.
150 -------------------
161 Field  1 -- # of reads issued
164 Field  2 -- # of sectors read
168 Field  3 -- # of writes issued
171 Field  4 -- # of sectors written
175 Note that since the address is translated to a disk-relative one, and no
176 record of the partition-relative address is kept, the subsequent success
190 keep record of the partition-relative address, an operation is attributed to
192 eventual merges. As requests can be merged across partition, this could lead
196 ----------------
199 Linux hasn't added it already, here's the line you'll want to add to
210 -- ricklind@us.ibm.com