perf intel-pt: Add documentation for Event Trace and TNT disable (24e3599c) · Commits · jan.koester / Linux

tools/perf/Documentation/perf-intel-pt.txt

+102 −2

Original line number	Diff line number	Diff line
		@@ -108,9 +108,10 @@ displayed as follows:

		perf script --itrace=ibxwpe -F+flags

		The flags are "bcrosyiABExgh" which stand for branch, call, return, conditional,
		The flags are "bcrosyiABExghDt" which stand for branch, call, return, conditional,
		system, asynchronous, interrupt, transaction abort, trace begin, trace end,
		in transaction, VM-entry, and VM-exit respectively.
		in transaction, VM-entry, VM-exit, interrupt disabled, and interrupt disable
		toggle respectively.

		perf script also supports higher level ways to dump instruction traces:

		@@ -483,6 +484,30 @@ pwr_evt Enable power events. The power events provide information about
		which contains "1" if the feature is supported and
		"0" otherwise.

		event Enable Event Trace. The events provide information about asynchronous
		events.

		Support for this feature is indicated by:

		/sys/bus/event_source/devices/intel_pt/caps/event_trace

		which contains "1" if the feature is supported and
		"0" otherwise.

		notnt Disable TNT packets. Without TNT packets, it is not possible to walk
		executable code to reconstruct control flow, however FUP, TIP, TIP.PGE
		and TIP.PGD packets still indicate asynchronous control flow, and (if
		return compression is disabled - see noretcomp) return statements.
		The advantage of eliminating TNT packets is reducing the size of the
		trace and corresponding tracing overhead.

		Support for this feature is indicated by:

		/sys/bus/event_source/devices/intel_pt/caps/tnt_disable

		which contains "1" if the feature is supported and
		"0" otherwise.


		AUX area sampling option
		~~~~~~~~~~~~~~~~~~~~~~~~
		@@ -876,6 +901,8 @@ The letters are:
		p synthesize "power" events (incl. PSB events)
		c synthesize branches events (calls only)
		r synthesize branches events (returns only)
		o synthesize PEBS-via-PT events
		I synthesize Event Trace events
		e synthesize tracing error events
		d create a debug log
		g synthesize a call chain (use with i or x)
		@@ -1371,6 +1398,79 @@ There were none.
		:17006 17006 [001] 11500.262869216: ffffffff8220116e error_entry+0xe ([guest.kernel.kallsyms]) pushq %rax


		Event Trace
		-----------

		Event Trace records information about asynchronous events, for example interrupts,
		faults, VM exits and entries. The information is recorded in CFE and EVD packets,
		and also the Interrupt Flag is recorded on the MODE.Exec packet. The CFE packet
		contains a type field to identify one of the following:

		1 INTR interrupt, fault, exception, NMI
		2 IRET interrupt return
		3 SMI system management interrupt
		4 RSM resume from system management mode
		5 SIPI startup interprocessor interrupt
		6 INIT INIT signal
		7 VMENTRY VM-Entry
		8 VMEXIT VM-Entry
		9 VMEXIT_INTR VM-Exit due to interrupt
		10 SHUTDOWN Shutdown

		For more details, refer to the Intel 64 and IA-32 Architectures Software
		Developer Manuals (version 076 or later).

		The capability to do Event Trace is indicated by the
		/sys/bus/event_source/devices/intel_pt/caps/event_trace file.

		Event trace is selected for recording using the "event" config term. e.g.

		perf record -e intel_pt/event/u uname

		Event trace events are output using the --itrace I option. e.g.

		perf script --itrace=Ie

		perf script displays events containing CFE type, vector and event data,
		in the form:

		evt: hw int (t) cfe: INTR IP: 1 vector: 3 PFA: 0x8877665544332211

		The IP flag indicates if the event binds to an IP, which includes any case where
		flow control packet generation is enabled, as well as when CFE packet IP bit is
		set.

		perf script displays events containing changes to the Interrupt Flag in the form:

		iflag: t IFLAG: 1->0 via branch

		where "via branch" indicates a branch (interrupt or return from interrupt) and
		"non branch" indicates an instruction such as CFI, STI or POPF).

		In addition, the current state of the interrupt flag is indicated by the presence
		or absence of the "D" (interrupt disabled) perf script flag. If the interrupt
		flag is changed, then the "t" flag is also included i.e.

		no flag, interrupts enabled IF=1
		t interrupts become disabled IF=1 -> IF=0
		D interrupts are disabled IF=0
		Dt interrupts become enabled IF=0 -> IF=1

		The intel-pt-events.py script illustrates how to access Event Trace information
		using a Python script.


		TNT Disable
		-----------

		TNT packets are disabled using the "notnt" config term. e.g.

		perf record -e intel_pt/notnt/u uname

		In that case the --itrace q option is forced because walking executable code
		to reconstruct the control flow is not possible.



		SEE ALSO
		--------