path: root/tools/perf/Documentation/perf-top.txt

perf-top(1)
===========

NAME
----
perf-top - System profiling tool.

SYNOPSIS
--------
[verse]
'perf top' [-e <EVENT> | --event=EVENT] [<options>]

DESCRIPTION
-----------
This command generates and displays a performance counter profile in real time.


OPTIONS
-------
-a::
--all-cpus::
        System-wide collection.  (default)

-c <count>::
--count=<count>::
	Event period to sample.

-C <cpu-list>::
--cpu=<cpu>::
Monitor only on the list of CPUs provided. Multiple CPUs can be provided as a
comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0-2.
Default is to monitor all CPUS.

-d <seconds>::
--delay=<seconds>::
	Number of seconds to delay between refreshes.

-e <event>::
--event=<event>::
	Select the PMU event. Selection can be a symbolic event name
	(use 'perf list' to list all events) or a raw PMU
	event (eventsel+umask) in the form of rNNN where NNN is a
	hexadecimal event descriptor.

-E <entries>::
--entries=<entries>::
	Display this many functions.

-f <count>::
--count-filter=<count>::
	Only display functions with more events than this.

--group::
        Put the counters into a counter group.

--group-sort-idx::
	Sort the output by the event at the index n in group. If n is invalid,
	sort by the first event. It can support multiple groups with different
	amount of events. WARNING: This should be used on grouped events.

-F <freq>::
--freq=<freq>::
	Profile at this frequency. Use 'max' to use the currently maximum
	allowed frequency, i.e. the value in the kernel.perf_event_max_sample_rate
	sysctl.

-i::
--inherit::
	Child tasks do not inherit counters.

-k <path>::
--vmlinux=<path>::
	Path to vmlinux.  Required for annotation functionality.

--ignore-vmlinux::
	Ignore vmlinux files.

--kallsyms=<file>::
	kallsyms pathname

-m <pages>::
--mmap-pages=<pages>::
	Number of mmap data pages (must be a power of two) or size
	specification with appended unit character - B/K/M/G. The
	size is rounded up to have nearest pages power of two value.

-p <pid>::
--pid=<pid>::
	Profile events on existing Process ID (comma separated list).

-t <tid>::
--tid=<tid>::
        Profile events on existing thread ID (comma separated list).

-u::
--uid=::
        Record events in threads owned by uid. Name or number.

-r <priority>::
--realtime=<priority>::
	Collect data with this RT SCHED_FIFO priority.

--sym-annotate=<symbol>::
        Annotate this symbol.

-K::
--hide_kernel_symbols::
        Hide kernel symbols.

-U::
--hide_user_symbols::
        Hide user symbols.

--demangle-kernel::
        Demangle kernel symbols.

-D::
--dump-symtab::
        Dump the symbol table used for profiling.

-v::
--verbose::
	Be more verbose (show counter open errors, etc).

-z::
--zero::
	Zero history across display updates.

-s::
--sort::
	Sort by key(s): pid, comm, dso, symbol, parent, srcline, weight,
	local_weight, abort, in_tx, transaction, overhead, sample, period.
	Please see description of --sort in the perf-report man page.

--fields=::
	Specify output field - multiple keys can be specified in CSV format.
	Following fields are available:
	overhead, overhead_sys, overhead_us, overhead_children, sample and period.
	Also it can contain any sort key(s).

	By default, every sort keys not specified in --field will be appended
	automatically.

-n::
--show-nr-samples::
	Show a column with the number of samples.

--show-total-period::
	Show a column with the sum of periods.

--dsos::
	Only consider symbols in these dsos.  This option will affect the
	percentage of the overhead column.  See --percentage for more info.

--comms::
	Only consider symbols in these comms.  This option will affect the
	percentage of the overhead column.  See --percentage for more info.

--symbols::
	Only consider these symbols.  This option will affect the
	percentage of the overhead column.  See --percentage for more info.

-M::
--disassembler-style=:: Set disassembler style for objdump.

--prefix=PREFIX::
--prefix-strip=N::
        Remove first N entries from source file path names in executables
        and add PREFIX. This allows to display source code compiled on systems
        with different file system layout.

--source::
	Interleave source code with assembly code. Enabled by default,
	disable with --no-source.

--asm-raw::
	Show raw instruction encoding of assembly instructions.

-g::
	Enables call-graph (stack chain/backtrace) recording.

--call-graph [mode,type,min[,limit],order[,key][,branch]]::
	Setup and enable call-graph (stack chain/backtrace) recording,
	implies -g.  See `--call-graph` section in perf-record and
	perf-report man pages for details.

--children::
	Accumulate callchain of children to parent entry so that then can
	show up in the output.  The output will have a new "Children" column
	and will be sorted on the data.  It requires -g/--call-graph option
	enabled.  See the `overhead calculation' section for more details.
	Enabled by default, disable with --no-children.

--max-stack::
	Set the stack depth limit when parsing the callchain, anything
	beyond the specified depth will be ignored. This is a trade-off
	between information loss and faster processing especially for
	workloads that can have a very long callchain stack.

	Default: /proc/sys/kernel/perf_event_max_stack when present, 127 otherwise.

--ignore-callees=<regex>::
        Ignore callees of the function(s) matching the given regex.
        This has the effect of collecting the callers of each such
        function into one place in the call-graph tree.

--percent-limit::
	Do not show entries which have an overhead under that percent.
	(Default: 0).

--percentage::
	Determine how to display the overhead percentage of filtered entries.
	Filters can be applied by --comms, --dsos and/or --symbols options and
	Zoom operations on the TUI (thread, dso, etc).

	"relative" means it's relative to filtered entries only so that the
	sum of shown entries will be always 100%. "absolute" means it retains
	the original value before and after the filter is applied.

-w::
--column-widths=<width[,width...]>::
	Force each column width to the provided list, for large terminal
	readability.  0 means no limit (default behavior).

--proc-map-timeout::
	When processing pre-existing threads /proc/XXX/mmap, it may take
	a long time, because the file may be huge. A time out is needed
	in such cases.
	This option sets the time out limit. The default value is 500 ms.


-b::
--branch-any::
	Enable taken branch stack sampling. Any type of taken branch may be sampled.
	This is a shortcut for --branch-filter any. See --branch-filter for more infos.

-j::
--branch-filter::
	Enable taken branch stack sampling. Each sample captures a series of consecutive
	taken branches. The number of branches captured with each sample depends on the
	underlying hardware, the type of branches of interest, and the executed code.
	It is possible to select the types of branches captured by enabling filters.
	For a full list of modifiers please see the perf record manpage.

	The option requires at least one branch type among any, any_call, any_ret, ind_call, cond.
	The privilege levels may be omitted, in which case, the privilege levels of the associated
	event are applied to the branch filter. Both kernel (k) and hypervisor (hv) privilege
	levels are subject to permissions.  When sampling on multiple events, branch stack sampling
	is enabled for all the sampling events. The sampled branch type is the same for all events.
	The various filters must be specified as a comma separated list: --branch-filter any_ret,u,k
	Note that this feature may not be available on all processors.

--raw-trace::
	When displaying traceevent output, do not use print fmt or plugins.

--hierarchy::
	Enable hierarchy output.

--overwrite::
	Enable this to use just the most recent records, which helps in high core count
	machines such as Knights Landing/Mill, but right now is disabled by default as
	the pausing used in this technique is leading to loss of metadata events such
	as PERF_RECORD_MMAP which makes 'perf top' unable to resolve samples, leading
	to lots of unknown samples appearing on the UI. Enable this if you are in such
	machines and profiling a workload that doesn't creates short lived threads and/or
	doesn't uses many executable mmap operations. Work is being planed to solve
	this situation, till then, this will remain disabled by default.

--force::
	Don't do ownership validation.

--num-thread-synthesize::
	The number of threads to run when synthesizing events for existing processes.
	By default, the number of threads equals to the number of online CPUs.

--namespaces::
	Record events of type PERF_RECORD_NAMESPACES and display it with the
	'cgroup_id' sort key.

--all-cgroups::
	Record events of type PERF_RECORD_CGROUP and display it with the
	'cgroup' sort key.

--switch-on EVENT_NAME::
	Only consider events after this event is found.

	E.g.:

           Find out where broadcast packets are handled

		perf probe -L icmp_rcv

	   Insert a probe there:

		perf probe icmp_rcv:59

	   Start perf top and ask it to only consider the cycles events when a
           broadcast packet arrives This will show a menu with two entries and
           will start counting when a broadcast packet arrives:

		perf top -e cycles,probe:icmp_rcv --switch-on=probe:icmp_rcv

	   Alternatively one can ask for --group and then two overhead columns
           will appear, the first for cycles and the second for the switch-on event.

		perf top --group -e cycles,probe:icmp_rcv --switch-on=probe:icmp_rcv

	This may be interesting to measure a workload only after some initialization
	phase is over, i.e. insert a perf probe at that point and use the above
	examples replacing probe:icmp_rcv with the just-after-init probe.

--switch-off EVENT_NAME::
	Stop considering events after this event is found.

--show-on-off-events::
	Show the --switch-on/off events too. This has no effect in 'perf top' now
	but probably we'll make the default not to show the switch-on/off events
        on the --group mode and if there is only one event besides the off/on ones,
	go straight to the histogram browser, just like 'perf top' with no events
	explicitely specified does.


INTERACTIVE PROMPTING KEYS
--------------------------

[d]::
	Display refresh delay.

[e]::
	Number of entries to display.

[E]::
	Event to display when multiple counters are active.

[f]::
	Profile display filter (>= hit count).

[F]::
	Annotation display filter (>= % of total).

[s]::
	Annotate symbol.

[S]::
	Stop annotation, return to full profile display.

[K]::
	Hide kernel symbols.

[U]::
	Hide user symbols.

[z]::
	Toggle event count zeroing across display updates.

[qQ]::
	Quit.

Pressing any unmapped key displays a menu, and prompts for input.

include::callchain-overhead-calculation.txt[]

SEE ALSO
--------
linkperf:perf-stat[1], linkperf:perf-list[1], linkperf:perf-report[1]