I originally posted this at http://dtrace.org/blogs/brendan/2011/03/08/dtrace-book-talk-sf.
Tomorrow (Wednesday, March 9th) I'll give a talk at SFOSUG about DTrace Book highlights, especially from Chapter 5 File Systems, which is available to download and read beforehand as a sample chapter. We'll also have one pre-print copy to give out to one lucky guest.
Here is a text-based screenshot of DTracing file systems to whet your appetite:
solaris# perturbation.d zfs_ioc_snapshot
Tracing ZFS perturbation by zfs_ioc_snapshot()... Ctrl-C to end.
^C
zfs_write normal (ms)
value ------------- Distribution ------------- count
-1 | 0
0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 348381
1 | 7
2 | 0
zfs_write during perturbation (ms)
value ------------- Distribution ------------- count
-1 | 0
0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 276029
1 | 11
2 | 5
4 | 0
zfs_ioc_snapshot perturbation duration (ms)
value ------------- Distribution ------------- count
512 | 0
1024 |@@@@@@@@@@@@@@@@@@@@@@@@@@@ 2
2048 |@@@@@@@@@@@@@ 1
4096 | 0
zfs_read during perturbation (ms)
value ------------- Distribution ------------- count
-1 | 0
0 |@ 5
1 | 0
2 | 0
4 | 3
8 |@@@@@@@@@@@@ 77
16 |@@@@@@@@@@@@@@@@@@ 117
32 |@@@@ 26
64 |@@ 16
128 |@ 8
256 | 2
512 |@ 5
1024 | 0
zfs_read normal (ms)
value ------------- Distribution ------------- count
-1 | 0
0 |@@@@ 97
1 | 0
2 | 0
4 |@ 29
8 |@@@@@@@@@@@@@@@@@@@@@@@@ 563
16 |@@@@@@@@@@ 241
32 | 10
64 | 1
128 | 0
But it won't all be text; here is a DTrace-based visualization of file system latency:
If you are interested in DTrace and are in San Francisco, come by and I'll see you there!
If you can't make it in person, it should be on ustream by Deirdré (ustream viewers are also eligible for the book drawing).