biosnoop.bt

#!/usr/bin/env bpftrace
/*
 * biosnoop.bt   Block I/O tracing tool, showing per I/O latency.
 *               For Linux, uses bpftrace, eBPF.
 *
 * TODO: switch to block tracepoints. Add device, offset, and size columns.
 *
 * This is a bpftrace version of the bcc tool of the same name.
 *
 * 15-Nov-2017	Brendan Gregg	Created this.
 */

BEGIN
{
	printf("%-12s %-16s %-6s %7s\n", "TIME(ms)", "COMM", "PID", "LAT(ms)");
	@epoch = nsecs;
}

kprobe:blk_account_io_start
{
	@start[arg0] = nsecs;
	@iopid[arg0] = pid;
	@iocomm[arg0] = comm;
}

kprobe:blk_account_io_completion
/@start[arg0] != 0 && @iopid[arg0] != 0 && @iocomm[arg0] != ""/

{
	$now = nsecs;
	printf("%-12u %-16s %-6d %7d\n",
	    ($now - @epoch) / 1000000, @iocomm[arg0], @iopid[arg0],
	    ($now - @start[arg0]) / 1000000);

	delete(@start[arg0]);
	delete(@iopid[arg0]);
	delete(@iocomm[arg0]);
}

END
{
	delete(@epoch);
}