dvmstat_example.txt [plain text]
The following is a demonstration of the dvmstat program,
Here we run dvmstat to monitor all processes called "find". In another
window, a "find /" command is run,
# dvmstat -n find
re maj mf fr epi epo api apo fpi fpo sy
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
6336 0 372 0 0 0 0 0 0 0 22255
1624 0 0 0 0 0 0 0 0 0 5497
2292 0 0 0 0 0 0 0 0 0 7715
13064 0 0 0 0 0 0 0 0 0 43998
7972 168 0 0 0 0 0 0 168 0 38361
468 636 0 0 0 0 0 0 636 0 13774
376 588 0 0 0 0 0 0 588 0 10723
80 636 0 0 0 0 0 0 656 0 11078
48 772 0 0 0 0 0 0 812 0 9841
16 1028 0 0 0 0 0 0 1056 0 10752
0 1712 0 0 0 0 0 0 1740 0 12176
4 1224 0 0 0 0 0 0 1236 0 9024
The output above is spectacular! When the find command is first run,
it begins be reading data from the file cache, as indicated by the "re"
reclaims, and a lack of "fpi" filesystem page ins.
Eventually the find command travels to places which are not cached, we can
see the "re" value drops, and both the "maj" major faults and "fpi" values
increase. This transition from cache hits to file system activity is
very clear from the above output.
Here we run a dvmstat to examine the PID 3778,
# dvmstat -p 3778
re maj mf fr epi epo api apo fpi fpo sy
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
24 28 0 0 0 0 0 0 28 0 109
4 148 16 0 0 0 0 0 148 0 1883
16 412 384 0 0 0 0 0 412 0 21019
0 0 0 0 0 0 0 0 0 0 3
0 0 0 0 0 0 0 0 0 0 221
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 84
0 0 0 0 0 0 0 0 0 0 0
Here we can see the statistics for that process only.
The following runs the date command through dvmstat,
# dvmstat date
Sun Jun 12 17:44:24 EST 2005
re maj mf fr epi epo api apo fpi fpo sy
16 0 208 0 0 0 0 0 0 0 38
The values above are for the date command only.
Now we run dvmstat on a tar command. Here we tar around 50Mb of files,
so the command takes around 20 seconds to complete,
# dvmstat tar cf backup.tar DTrace
re maj mf fr epi epo api apo fpi fpo sy
20 256 304 0 8 0 0 0 352 0 621
4540 56 896 0 0 0 0 0 4636 0 1005
4432 12 644 0 0 0 0 0 4384 0 906
680 180 136 0 8 0 0 0 1056 0 502
2328 60 468 0 0 0 0 0 2296 0 592
1300 380 272 0 0 0 0 0 1704 0 1095
2816 72 560 0 0 0 0 0 2940 0 709
4084 40 416 0 0 0 0 0 4220 0 894
2764 4 276 0 0 0 0 0 2700 0 566
1824 96 328 0 0 0 0 0 2072 0 556
3408 80 392 0 20 0 0 0 3496 0 857
2804 92 552 0 4 0 0 0 2924 0 741
1344 16 272 0 0 0 0 0 1376 0 289
3284 52 520 0 12 0 0 0 3260 0 743
4832 200 812 0 0 0 0 0 5292 0 1276
11052 56 2200 0 0 0 0 0 8676 0 2326
5256 328 1020 0 8 0 0 0 4404 0 1725
re maj mf fr epi epo api apo fpi fpo sy
404 340 72 0 64 0 0 0 536 0 1135
Great! Activity from the tar command such as "fpi"s can be clearly seen.