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biosnoop_example.txt

Demonstrations of biosnoop, the Linux BPF/bpftrace version. This traces block I/O, and shows the issuing process (at least, the process that was on-CPU at the time of queue insert) and the latency of the I/O: # ./biosnoop.bt Attaching 4 probes... TIME(ms) DISK COMM PID LAT(ms) 611 nvme0n1 bash 4179 10 611 nvme0n1 cksum 4179 0 627 nvme0n1 cksum 4179 15 641 nvme0n1 cksum 4179 13 644 nvme0n1 cksum 4179 3 658 nvme0n1 cksum 4179 13 673 nvme0n1 cksum 4179 14 686 nvme0n1 cksum 4179 13 701 nvme0n1 cksum 4179 14 710 nvme0n1 cksum 4179 8 717 nvme0n1 cksum 4179 6 728 nvme0n1 cksum 4179 10 735 nvme0n1 cksum 4179 6 751 nvme0n1 cksum 4179 10 758 nvme0n1 cksum 4179 17 783 nvme0n1 cksum 4179 12 796 nvme0n1 cksum 4179 25 802 nvme0n1 cksum 4179 32 [...] This output shows the cksum process was issuing block I/O, which were completing with around 12 milliseconds of latency. Each block I/O event is printed out, with a completion time as the first column, measured from program start. An example of some background flushing: # ./biosnoop.bt Attaching 4 probes... TIME(ms) DISK COMM PID LAT(ms) 2966 nvme0n1 jbd2/nvme0n1-8 615 0 2967 nvme0n1 jbd2/nvme0n1-8 615 0 [...] There is another version of this tool in bcc: https://github.com/iovisor/bcc The bcc version provides more fields.

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docroot: /var/www/469ed2f6-4d4b-4a8a-9f5e-ee4ef04d3bc8/public_html

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curdir: /usr/share/doc/bpftrace/examples

	.		4096
	..		4096
X	bashreadline_example.txt		722
X	biolatency_example.txt		1790
X	biosnoop_example.txt		2056
X	biostacks_example.txt		1914
X	bitesize_example.txt		3003
X	capable_example.txt		2659
X	cpuwalk_example.txt		4919
X	dcsnoop_example.txt		4612
X	execsnoop_example.txt		1535
X	gethostlatency_example.txt		923
X	killsnoop_example.txt		846
X	loads_example.txt		864
X	mdflush_example.txt		1866
X	naptime_example.txt		844
X	oomkill_example.txt		1668
X	opensnoop_example.txt		2528
X	pidpersec_example.txt		1504
X	runqlat_example.txt		8632
X	runqlen_example.txt		980
X	setuids_example.txt		2441
X	ssllatency_example.txt		4510
X	sslsnoop_example.txt		1916
X	statsnoop_example.txt		2738
X	swapin_example.txt		549
X	syncsnoop_example.txt		541
X	syscount_example.txt		1144
X	tcpaccept_example.txt		1350
X	tcpconnect_example.txt		1085
X	tcpdrop_example.txt		1256
X	tcplife_example.txt		1597
X	tcpretrans_example.txt		1153
X	tcpsynbl_example.txt		940
X	threadsnoop_example.txt		1182
X	undump_example.txt		680
X	vfscount_example.txt		1199
X	vfsstat_example.txt		929
X	writeback_example.txt		1962
X	xfsdist_example.txt		3419