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PERF_5.6-REPORT(1) perf Manual PERF_5.6-REPORT(1)

NAME

perf-report - Read perf.data (created by perf record) and display the profile

SYNOPSIS

perf report [-i <file> | --input=file]

DESCRIPTION

This command displays the performance counter profile information recorded via perf record.

OPTIONS

-i, --input=
Input file name. (default: perf.data unless stdin is a fifo)

-v, --verbose

Be more verbose. (show symbol address, etc)

-q, --quiet

Do not show any message. (Suppress -v)

-n, --show-nr-samples

Show the number of samples for each symbol

--show-cpu-utilization

Show sample percentage for different cpu modes.

-T, --threads

Show per-thread event counters. The input data file should be recorded with -s option.

-c, --comms=

Only consider symbols in these comms. CSV that understands <file://filename> entries. This option will affect the percentage of the overhead column. See --percentage for more info.

--pid=

Only show events for given process ID (comma separated list).

--tid=

Only show events for given thread ID (comma separated list).

-d, --dsos=

Only consider symbols in these dsos. CSV that understands <file://filename> entries. This option will affect the percentage of the overhead column. See --percentage for more info.

-S, --symbols=

Only consider these symbols. CSV that understands <file://filename> entries. This option will affect the percentage of the overhead column. See --percentage for more info.

--symbol-filter=

Only show symbols that match (partially) with this filter.

-U, --hide-unresolved

Only display entries resolved to a symbol.

-s, --sort=

Sort histogram entries by given key(s) - multiple keys can be specified in CSV format. Following sort keys are available: pid, comm, dso, symbol, parent, cpu, socket, srcline, weight, local_weight, cgroup_id.

Each key has following meaning:

•comm: command (name) of the task which can be read via /proc/<pid>/comm

•pid: command and tid of the task

•dso: name of library or module executed at the time of sample

•dso_size: size of library or module executed at the time of sample

•symbol: name of function executed at the time of sample

•symbol_size: size of function executed at the time of sample

•parent: name of function matched to the parent regex filter. Unmatched entries are displayed as "[other]".

•cpu: cpu number the task ran at the time of sample

•socket: processor socket number the task ran at the time of sample

•srcline: filename and line number executed at the time of sample. The DWARF debugging info must be provided.

•srcfile: file name of the source file of the samples. Requires dwarf information.

•weight: Event specific weight, e.g. memory latency or transaction abort cost. This is the global weight.

•local_weight: Local weight version of the weight above.

•cgroup_id: ID derived from cgroup namespace device and inode numbers.

•transaction: Transaction abort flags.

•overhead: Overhead percentage of sample

•overhead_sys: Overhead percentage of sample running in system mode

•overhead_us: Overhead percentage of sample running in user mode

•overhead_guest_sys: Overhead percentage of sample running in system mode on guest machine

•overhead_guest_us: Overhead percentage of sample running in user mode on guest machine

•sample: Number of sample

•period: Raw number of event count of sample

•time: Separate the samples by time stamp with the resolution specified by --time-quantum (default 100ms). Specify with overhead and before it.

By default, comm, dso and symbol keys are used.
(i.e. --sort comm,dso,symbol)

If --branch-stack option is used, following sort keys are also
available:

•dso_from: name of library or module branched from

•dso_to: name of library or module branched to

•symbol_from: name of function branched from

•symbol_to: name of function branched to

•srcline_from: source file and line branched from

•srcline_to: source file and line branched to

•mispredict: "N" for predicted branch, "Y" for mispredicted branch

•in_tx: branch in TSX transaction

•abort: TSX transaction abort.

•cycles: Cycles in basic block

And default sort keys are changed to comm, dso_from, symbol_from, dso_to
and symbol_to, see '--branch-stack'.

When the sort key symbol is specified, columns "IPC" and "IPC Coverage"
are enabled automatically. Column "IPC" reports the average IPC per function
and column "IPC coverage" reports the percentage of instructions with
sampled IPC in this function. IPC means Instruction Per Cycle. If it's low,
it indicates there may be a performance bottleneck when the function is
executed, such as a memory access bottleneck. If a function has high overhead
and low IPC, it's worth further analyzing it to optimize its performance.

If the --mem-mode option is used, the following sort keys are also available
(incompatible with --branch-stack):
symbol_daddr, dso_daddr, locked, tlb, mem, snoop, dcacheline.

•symbol_daddr: name of data symbol being executed on at the time of sample

•dso_daddr: name of library or module containing the data being executed on at the time of the sample

•locked: whether the bus was locked at the time of the sample

•tlb: type of tlb access for the data at the time of the sample

•mem: type of memory access for the data at the time of the sample

•snoop: type of snoop (if any) for the data at the time of the sample

•dcacheline: the cacheline the data address is on at the time of the sample

•phys_daddr: physical address of data being executed on at the time of sample

And the default sort keys are changed to local_weight, mem, sym, dso,
symbol_daddr, dso_daddr, snoop, tlb, locked, see '--mem-mode'.

If the data file has tracepoint event(s), following (dynamic) sort keys
are also available:
trace, trace_fields, [<event>.]<field>[/raw]

•trace: pretty printed trace output in a single column

•trace_fields: fields in tracepoints in separate columns

•<field name>: optional event and field name for a specific field

The last form consists of event and field names.  If event name is
omitted, it searches all events for matching field name.  The matched
field will be shown only for the event has the field.  The event name
supports substring match so user doesn't need to specify full subsystem
and event name everytime.  For example, 'sched:sched_switch' event can
be shortened to 'switch' as long as it's not ambiguous.  Also event can
be specified by its index (starting from 1) preceded by the '%'.
So '%1' is the first event, '%2' is the second, and so on.

The field name can have '/raw' suffix which disables pretty printing
and shows raw field value like hex numbers.  The --raw-trace option
has the same effect for all dynamic sort keys.

The default sort keys are changed to 'trace' if all events in the data
file are tracepoint.

-F, --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 -F will be appended
automatically.

If the keys starts with a prefix '+', then it will append the specified
       field(s) to the default field order. For example: perf report -F +period,sample.

-p, --parent=<regex>

A regex filter to identify parent. The parent is a caller of this function and searched through the callchain, thus it requires callchain information recorded. The pattern is in the extended regex format and defaults to "^sys_|^do_page_fault", see --sort parent.

-x, --exclude-other

Only display entries with parent-match.

-w, --column-widths=<width[,width...]>

Force each column width to the provided list, for large terminal readability. 0 means no limit (default behavior).

-t, --field-separator=

Use a special separator character and don’t pad with spaces, replacing all occurrences of this separator in symbol names (and other output) with a . character, that thus it’s the only non valid separator.

-D, --dump-raw-trace

Dump raw trace in ASCII.

-g, --call-graph=<print_type,threshold[,print_limit],order,sort_key[,branch],value>

Display call chains using type, min percent threshold, print limit, call order, sort key, optional branch and value. Note that ordering is not fixed so any parameter can be given in an arbitrary order. One exception is the print_limit which should be preceded by threshold.

print_type can be either:
- flat: single column, linear exposure of call chains.
- graph: use a graph tree, displaying absolute overhead rates. (default)
- fractal: like graph, but displays relative rates. Each branch of
         the tree is considered as a new profiled object.
- folded: call chains are displayed in a line, separated by semicolons
- none: disable call chain display.

threshold is a percentage value which specifies a minimum percent to be
included in the output call graph.  Default is 0.5 (%).

print_limit is only applied when stdio interface is used.  It's to limit
number of call graph entries in a single hist entry.  Note that it needs
to be given after threshold (but not necessarily consecutive).
Default is 0 (unlimited).

order can be either:
- callee: callee based call graph.
- caller: inverted caller based call graph.
Default is 'caller' when --children is used, otherwise 'callee'.

sort_key can be:
- function: compare on functions (default)
- address: compare on individual code addresses
- srcline: compare on source filename and line number

branch can be:
- branch: include last branch information in callgraph when available.
          Usually more convenient to use --branch-history for this.

value can be:
- percent: display overhead percent (default)
- period: display event period
- count: display event count

--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 callchains are recorded. 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. Note that when using the --itrace option the synthesized callchain size will override this value if the synthesized callchain size is bigger.

Default: 127

-G, --inverted

alias for inverted caller based call graph.

--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.

--pretty=<key>

Pretty printing style. key: normal, raw

--stdio

Use the stdio interface.

--stdio-color

always, never or auto, allowing configuring color output via the command line, in addition to via "color.ui" .perfconfig. Use --stdio-color always to generate color even when redirecting to a pipe or file. Using just --stdio-color is equivalent to using always.

--tui

Use the TUI interface, that is integrated with annotate and allows zooming into DSOs or threads, among other features. Use of --tui requires a tty, if one is not present, as when piping to other commands, the stdio interface is used.

--gtk

Use the GTK2 interface.

-k, --vmlinux=<file>

vmlinux pathname

--ignore-vmlinux

Ignore vmlinux files.

--kallsyms=<file>

kallsyms pathname

-m, --modules

Load module symbols. WARNING: This should only be used with -k and a LIVE kernel.

-f, --force

Don’t do ownership validation.

--symfs=<directory>

Look for files with symbols relative to this directory.

-C, --cpu

Only report samples for 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 report samples on all CPUs.

-M, --disassembler-style=

Set disassembler style for objdump.

--source

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

--asm-raw

Show raw instruction encoding of assembly instructions.

--show-total-period

Show a column with the sum of periods.

-I, --show-info

Display extended information about the perf.data file. This adds information which may be very large and thus may clutter the display. It currently includes: cpu and numa topology of the host system.

-b, --branch-stack

Use the addresses of sampled taken branches instead of the instruction address to build the histograms. To generate meaningful output, the perf.data file must have been obtained using perf record -b or perf record --branch-filter xxx where xxx is a branch filter option. perf report is able to auto-detect whether a perf.data file contains branch stacks and it will automatically switch to the branch view mode, unless --no-branch-stack is used.

--branch-history

Add the addresses of sampled taken branches to the callstack. This allows to examine the path the program took to each sample. The data collection must have used -b (or -j) and -g.

--objdump=<path>

Path to objdump binary.

--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.

--group

Show event group information together. It forces group output also if there are no groups defined in data file.

--demangle

Demangle symbol names to human readable form. It’s enabled by default, disable with --no-demangle.

--demangle-kernel

Demangle kernel symbol names to human readable form (for C++ kernels).

--mem-mode

Use the data addresses of samples in addition to instruction addresses to build the histograms. To generate meaningful output, the perf.data file must have been obtained using perf record -d -W and using a special event -e cpu/mem-loads/p or -e cpu/mem-stores/p. See perf mem for simpler access.

--percent-limit

Do not show entries which have an overhead under that percent. (Default: 0). Note that this option also sets the percent limit (threshold) of callchains. However the default value of callchain threshold is different than the default value of hist entries. Please see the --call-graph option for details.

--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.

--header

Show header information in the perf.data file. This includes various information like hostname, OS and perf version, cpu/mem info, perf command line, event list and so on. Currently only --stdio output supports this feature.

--header-only

Show only perf.data header (forces --stdio).

--time

Only analyze samples within given time window: <start>,<stop>. Times have the format seconds.nanoseconds. If start is not given (i.e. time string is ,x.y) then analysis starts at the beginning of the file. If stop time is not given (i.e. time string is x.y,) then analysis goes to end of file. Multiple ranges can be separated by spaces, which requires the argument to be quoted e.g. --time "1234.567,1234.789 1235,"

Also support time percent with multiple time ranges. Time string is
'a%/n,b%/m,...' or 'a%-b%,c%-%d,...'.

For example:
Select the second 10% time slice:

perf report --time 10%/2

Select from 0% to 10% time slice:

perf report --time 0%-10%

Select the first and second 10% time slices:

perf report --time 10%/1,10%/2

Select from 0% to 10% and 30% to 40% slices:

perf report --time 0%-10%,30%-40%

--switch-on EVENT_NAME

Only consider events after this event is found.

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 then using this
option with that 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 report 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 report with no events explicitely specified does.

--itrace

Options for decoding instruction tracing data. The options are:

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)
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.

To disable decoding entirely, use --no-itrace.

--full-source-path

Show the full path for source files for srcline output.

--show-ref-call-graph

When multiple events are sampled, it may not be needed to collect callgraphs for all of them. The sample sites are usually nearby, and it’s enough to collect the callgraphs on a reference event. So user can use "call-graph=no" event modifier to disable callgraph for other events to reduce the overhead. However, perf report cannot show callgraphs for the event which disable the callgraph. This option extends the perf report to show reference callgraphs, which collected by reference event, in no callgraph event.

--socket-filter

Only report the samples on the processor socket that match with this filter

--samples=N

Save N individual samples for each histogram entry to show context in perf report tui browser.

--raw-trace

When displaying traceevent output, do not use print fmt or plugins.

--hierarchy

Enable hierarchical output.

--inline

If a callgraph address belongs to an inlined function, the inline stack will be printed. Each entry is function name or file/line. Enabled by default, disable with --no-inline.

--mmaps

Show --tasks output plus mmap information in a format similar to /proc/<PID>/maps.

Please note that not all mmaps are stored, options affecting which ones
are include 'perf record --data', for instance.

--ns

Show time stamps in nanoseconds.

--stats

Display overall events statistics without any further processing. (like the one at the end of the perf report -D command)

--tasks

Display monitored tasks stored in perf data. Displaying pid/tid/ppid plus the command string aligned to distinguish parent and child tasks.

--percent-type

Set annotation percent type from following choices: global-period, local-period, global-hits, local-hits

The local/global keywords set if the percentage is computed
in the scope of the function (local) or the whole data (global).
The period/hits keywords set the base the percentage is computed
on - the samples period or the number of samples (hits).

--time-quantum

Configure time quantum for time sort key. Default 100ms. Accepts s, us, ms, ns units.

--total-cycles

When --total-cycles is specified, it supports sorting for all blocks by Sampled Cycles%. This is useful to concentrate on the globally hottest blocks. In output, there are some new columns:

'Sampled Cycles%' - block sampled cycles aggregation / total sampled cycles
'Sampled Cycles'  - block sampled cycles aggregation
'Avg Cycles%'     - block average sampled cycles / sum of total block average
                    sampled cycles
'Avg Cycles'      - block average sampled cycles

OVERHEAD CALCULATION

The overhead can be shown in two columns as Children and Self when perf collects callchains. The self overhead is simply calculated by adding all period values of the entry - usually a function (symbol). This is the value that perf shows traditionally and sum of all the self overhead values should be 100%.

The children overhead is calculated by adding all period values of the child functions so that it can show the total overhead of the higher level functions even if they don’t directly execute much. Children here means functions that are called from another (parent) function.

It might be confusing that the sum of all the children overhead values exceeds 100% since each of them is already an accumulation of self overhead of its child functions. But with this enabled, users can find which function has the most overhead even if samples are spread over the children.

Consider the following example; there are three functions like below.

void foo(void) {
    /* do something */
}
void bar(void) {
    /* do something */
    foo();
}
int main(void) {
    bar()
    return 0;
}

In this case foo is a child of bar, and bar is an immediate child of main so foo also is a child of main. In other words, main is a parent of foo and bar, and bar is a parent of foo.

Suppose all samples are recorded in foo and bar only. When it’s recorded with callchains the output will show something like below in the usual (self-overhead-only) output of perf report:

Overhead  Symbol
........  .....................
  60.00%  foo
          |
          --- foo
              bar
              main
              __libc_start_main
  40.00%  bar
          |
          --- bar
              main
              __libc_start_main

When the --children option is enabled, the self overhead values of child functions (i.e. foo and bar) are added to the parents to calculate the children overhead. In this case the report could be displayed as:

Children      Self  Symbol
........  ........  ....................
 100.00%     0.00%  __libc_start_main
          |
          --- __libc_start_main
 100.00%     0.00%  main
          |
          --- main
              __libc_start_main
 100.00%    40.00%  bar
          |
          --- bar
              main
              __libc_start_main
  60.00%    60.00%  foo
          |
          --- foo
              bar
              main
              __libc_start_main

In the above output, the self overhead of foo (60%) was add to the children overhead of bar, main and _\_libc_start_main. Likewise, the self overhead of bar (40%) was added to the children overhead of main and \_\_libc_start_main.

So \_\_libc_start_main and main are shown first since they have same (100%) children overhead (even though they have zero self overhead) and they are the parents of foo and bar.

Since v3.16 the children overhead is shown by default and the output is sorted by its values. The children overhead is disabled by specifying --no-children option on the command line or by adding report.children = false or top.children = false in the perf config file.

SEE ALSO

perf-stat(1), perf-annotate(1), perf-record(1)
2020-04-17 perf