tools/perf/Documentation/itrace.txt

		i	synthesize instructions events
		b	synthesize branches events
		c	synthesize branches events (calls only)
		r	synthesize branches events (returns only)
		x	synthesize transactions events
		w	synthesize ptwrite events
		p	synthesize power events
		o	synthesize other events recorded due to the use
			of aux-output (refer to perf record)
		e	synthesize error events
		d	create a debug log
		g	synthesize a call chain (use with i or x)
		G	synthesize a call chain on existing event records
		l	synthesize last branch entries (use with i or x)
		s       skip initial number of events

	The default is all events i.e. the same as --itrace=ibxwpe,
	except for perf script where it is --itrace=ce

	In addition, the period (default 100000, except for perf script where it is 1)
	for instructions events can be specified in units of:

		i	instructions
		t	ticks
		ms	milliseconds
		us	microseconds
		ns	nanoseconds (default)

	Also the call chain size (default 16, max. 1024) for instructions or
	transactions events can be specified.

	Also the number of last branch entries (default 64, max. 1024) for
	instructions or transactions events can be specified.

	It is also possible to skip events generated (instructions, branches, transactions,
	ptwrite, power) at the beginning. This is useful to ignore initialization code.

	--itrace=i0nss1000000

	skips the first million instructions.