bcc-scripts/biostat_example.txt at master · mcaleavya/bcc-scripts · GitHub

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Example file for biostat.py

# ./biostat.py

Device   r/s      w/s      rkb      wkb      rsz      wsz
sdb      0        13       0.00     52.00    0        4096
sdb      0        87       0.00     43.50    0        512


We can see that above we have the count of reads & writes, we also have the read & write blocks. We also show each type of i/o size
for each count.

iostat -xkz 1 |grep sd
Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sdb               0.00     0.00    0.00  100.00     0.00    95.50     1.91     0.04    0.44    0.00    0.44   0.44   4.40

so (13 * 4096) + ( 87 * 512 ) - 97792 / 1024 = 95.5

This matches with iostat , the formatting needs fixed.

Looking at biosnoop to compare.
iostat data
Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sdb               0.00     0.00    0.00  100.00     0.00    95.50     1.91     0.04    0.40    0.00    0.40   0.40   4.00

biosnoop.py > b1.log

s# awk '/dd/{print $7}' b.log |sort -u
4096
512
root@vm000826:/var/tmp/git/bcc/tools# awk '/dd/{print $7}' b.log |grep -wc 512
87
root@vm000826:/var/tmp/git/bcc/tools# awk '/dd/{print $7}' b.log |grep -wc 4096
13

Checking reads
# echo 1 > /proc/sys/vm/drop_caches
root@vm000826:/mnt# dd if=tfile of=/dev/null count=100
100+0 records in
100+0 records out
51200 bytes (51 kB) copied, 0.00393662 s, 13.0 MB/s

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00     0.00    8.00    0.00   200.00     0.00    50.00     0.00    0.50    0.50    0.00   0.50   0.40
sdb               0.00     0.00    4.00    0.00   240.00     0.00   120.00     0.00    0.00    0.00    0.00   0.00   0.00


We are interested in sdb as thats where we have our data

sda      1        0        28.00    0.00     28672    0
sda      1        0        80.00    0.00     81920    0
sdb      1        0        32.00    0.00     32768    0
sda      1        0        44.00    0.00     45056    0
sda      1        0        8.00     0.00     8192     0
sdb      1        0        128.00   0.00     131072   0
sdb      1        0        64.00    0.00     65536    0
sdb      1        0        16.00    0.00     16384    0
sda      2        0        8.00     0.00     4096     0
sda      2        0        32.00    0.00     16384    0


When we sum the 32 + 128 + 64 + 16 = 240kb which also matches iostat data. ( looking at iosnoop)

# grep dd b2.log  |grep sdb
0.480600000    dd             29591  sdb     R  3555328   16384      0.34
0.481165000    dd             29591  sdb     R  3555360   32768      0.52
0.481539000    dd             29591  sdb     R  3555424   65536      0.78
0.482431000    dd             29591  sdb     R  3555552   131072     1.13

This also matches our biostat counts.


---- Latency
Device   r/s      w/s      r/Kb       w/Kb       rsz      wsz      r_ms       w_ms
sda      0        1        0.00       4.00       0        4096     0.00       0.00
sda      0        1        0.00       56.00      0        57344    0.00       1.00
sdb      0        1        0.00       8.00       0        8192     0.00       2.00
sdb      0        999      0.00       7992.00    0        8192     0.00       0.00
sdb      0        1        0.00       4.00       0        4096     0.00       0.00
sdb      0        1        0.00       24.00      0        24576    0.00       0.00