biosnoop.bt

#!/usr/bin/env bpftrace
/*
 * biosnoop.bt   Block I/O tracing tool, showing per I/O latency.
 *               For Linux, uses bpftrace, eBPF.
 *
 * TODO: Add offset and size columns.
 *
 * This is a bpftrace version of the bcc tool of the same name.
 */

BEGIN
{
	printf("%-12s %-14s %-16s %-6s %7s\n",
		   "TIME(ms)", "DISK ID", "COMM", "PID", "LAT(ms)");
	printf("             MAJOR MINOR\n")
}

tracepoint:block:block_io_start
{
	$key = (args.dev, args.sector);
	@start[$key] = nsecs;
	@iopid[$key] = pid;
}

tracepoint:block:block_io_done
/@start[args.dev, args.sector] != 0 && @iopid[args.dev, args.sector] != 0 && args.comm != ""/

{
	$key = (args.dev, args.sector);
	$now = nsecs;
	$major = args.dev >> 20;
	$minor = args.dev & ((1 << 20) - 1);
	printf("%-12u %-5d %-8d %-16s %-6d %7d\n",
	    elapsed / 1e6, $major, $minor, args.comm, @iopid[$key],
	    ($now - @start[$key]) / 1e6);

	delete(@start, $key);
	delete(@iopid, $key);
}

END
{
	clear(@start);
	clear(@iopid);
}