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/usr/share/doc/bpftrace/examples

Name	Size	Mode	Actions
bashreadline_example.txt	722	0644	edit dl rm
biolatency_example.txt	1790	0644	edit dl rm
biosnoop_example.txt	2056	0644	edit dl rm
biostacks_example.txt	1914	0644	edit dl rm
bitesize_example.txt	3003	0644	edit dl rm
capable_example.txt	2659	0644	edit dl rm
cpuwalk_example.txt	4919	0644	edit dl rm
dcsnoop_example.txt	4612	0644	edit dl rm
execsnoop_example.txt	1535	0644	edit dl rm
gethostlatency_example.txt	923	0644	edit dl rm
killsnoop_example.txt	846	0644	edit dl rm
loads_example.txt	864	0644	edit dl rm
mdflush_example.txt	1866	0644	edit dl rm
naptime_example.txt	844	0644	edit dl rm
oomkill_example.txt	1668	0644	edit dl rm
opensnoop_example.txt	2528	0644	edit dl rm
pidpersec_example.txt	1504	0644	edit dl rm
runqlat_example.txt	8632	0644	edit dl rm
runqlen_example.txt	980	0644	edit dl rm
setuids_example.txt	2441	0644	edit dl rm
ssllatency_example.txt	4510	0644	edit dl rm
sslsnoop_example.txt	1916	0644	edit dl rm
statsnoop_example.txt	2738	0644	edit dl rm
swapin_example.txt	549	0644	edit dl rm
syncsnoop_example.txt	541	0644	edit dl rm
syscount_example.txt	1144	0644	edit dl rm
tcpaccept_example.txt	1350	0644	edit dl rm
tcpconnect_example.txt	1085	0644	edit dl rm
tcpdrop_example.txt	1256	0644	edit dl rm
tcplife_example.txt	1597	0644	edit dl rm
tcpretrans_example.txt	1153	0644	edit dl rm
tcpsynbl_example.txt	940	0644	edit dl rm
threadsnoop_example.txt	1182	0644	edit dl rm
undump_example.txt	680	0644	edit dl rm
vfscount_example.txt	1199	0644	edit dl rm
vfsstat_example.txt	929	0644	edit dl rm
writeback_example.txt	1962	0644	edit dl rm
xfsdist_example.txt	3419	0644	edit dl rm

Edit: /usr/share/doc/bpftrace/examples/mdflush_example.txt (1866B)

Demonstrations of mdflush, the Linux bpftrace/eBPF version.

The mdflush tool traces flushes at the md driver level, and prints details
including the time of the flush:

# ./mdflush.bt
Tracing md flush requests... Hit Ctrl-C to end.
TIME     PID    COMM             DEVICE
03:13:49 16770  sync             md0
03:14:08 16864  sync             md0
03:14:49 496    kworker/1:0H     md0
03:14:49 488    xfsaild/md0      md0
03:14:54 488    xfsaild/md0      md0
03:15:00 488    xfsaild/md0      md0
03:15:02 85     kswapd0          md0
03:15:02 488    xfsaild/md0      md0
03:15:05 488    xfsaild/md0      md0
03:15:08 488    xfsaild/md0      md0
03:15:10 488    xfsaild/md0      md0
03:15:11 488    xfsaild/md0      md0
03:15:11 488    xfsaild/md0      md0
03:15:11 488    xfsaild/md0      md0
03:15:11 488    xfsaild/md0      md0
03:15:11 488    xfsaild/md0      md0
03:15:12 488    xfsaild/md0      md0
03:15:13 488    xfsaild/md0      md0
03:15:15 488    xfsaild/md0      md0
03:15:19 496    kworker/1:0H     md0
03:15:49 496    kworker/1:0H     md0
03:15:55 18840  sync             md0
03:16:49 496    kworker/1:0H     md0
03:17:19 496    kworker/1:0H     md0
03:20:19 496    kworker/1:0H     md0
03:21:19 496    kworker/1:0H     md0
03:21:49 496    kworker/1:0H     md0
03:25:19 496    kworker/1:0H     md0
[...]

This can be useful for correlation with latency outliers or spikes in disk
latency, as measured using another tool (eg, system monitoring). If spikes in
disk latency often coincide with md flush events, then it would make flushing
a target for tuning.

Note that the flush events are likely to originate from higher in the I/O
stack, such as from file systems. This traces md processing them, and the
timestamp corresponds with when md began to issue the flush to disks.

There is another version of this tool in bcc: https://github.com/iovisor/bcc

cmd: