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b50311dc2a
This patch adds support for taken branch sampling, i.e, the
PERF_SAMPLE_BRANCH_STACK feature to perf report. In other
words, to display histograms based on taken branches rather
than executed instructions addresses.
The new option is called -b and it takes no argument. To
generate meaningful output, the perf.data must have been
obtained using perf record -b xxx ... where xxx is a branch
filter option.
The output shows symbols, modules, sorted by 'who branches
where' the most often. The percentages reported in the first
column refer to the total number of branches captured and
not the usual number of samples.
Here is a quick example.
Here branchy is simple test program which looks as follows:
void f2(void)
{}
void f3(void)
{}
void f1(unsigned long n)
{
if (n & 1UL)
f2();
else
f3();
}
int main(void)
{
unsigned long i;
for (i=0; i < N; i++)
f1(i);
return 0;
}
Here is the output captured on Nehalem, if we are
only interested in user level function calls.
$ perf record -b any_call,u -e cycles:u branchy
$ perf report -b --sort=symbol
52.34% [.] main [.] f1
24.04% [.] f1 [.] f3
23.60% [.] f1 [.] f2
0.01% [k] _IO_new_file_xsputn [k] _IO_file_overflow
0.01% [k] _IO_vfprintf_internal [k] _IO_new_file_xsputn
0.01% [k] _IO_vfprintf_internal [k] strchrnul
0.01% [k] __printf [k] _IO_vfprintf_internal
0.01% [k] main [k] __printf
About half (52%) of the call branches captured are from main()
-> f1(). The second half (24%+23%) is split in two equal shares
between f1() -> f2(), f1() ->f3(). The output is as expected
given the code.
It should be noted, that using -b in perf record does not
eliminate information in the perf.data file. Consequently, a
typical profile can also be obtained by perf report by simply
not using its -b option.
It is possible to sort on branch related columns:
- dso_from, symbol_from
- dso_to, symbol_to
- mispredict
Signed-off-by: Roberto Agostino Vitillo <ravitillo@lbl.gov>
Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: peterz@infradead.org
Cc: acme@redhat.com
Cc: robert.richter@amd.com
Cc: ming.m.lin@intel.com
Cc: andi@firstfloor.org
Cc: asharma@fb.com
Cc: vweaver1@eecs.utk.edu
Cc: khandual@linux.vnet.ibm.com
Cc: dsahern@gmail.com
Link: http://lkml.kernel.org/r/1328826068-11713-14-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
165 lines
4 KiB
Text
165 lines
4 KiB
Text
perf-report(1)
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==============
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NAME
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----
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perf-report - Read perf.data (created by perf record) and display the profile
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SYNOPSIS
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--------
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[verse]
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'perf report' [-i <file> | --input=file]
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DESCRIPTION
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-----------
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This command displays the performance counter profile information recorded
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via perf record.
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OPTIONS
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-------
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-i::
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--input=::
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Input file name. (default: perf.data unless stdin is a fifo)
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-v::
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--verbose::
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Be more verbose. (show symbol address, etc)
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-d::
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--dsos=::
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Only consider symbols in these dsos. CSV that understands
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file://filename entries.
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-n::
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--show-nr-samples::
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Show the number of samples for each symbol
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--showcpuutilization::
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Show sample percentage for different cpu modes.
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-T::
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--threads::
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Show per-thread event counters
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-c::
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--comms=::
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Only consider symbols in these comms. CSV that understands
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file://filename entries.
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-S::
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--symbols=::
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Only consider these symbols. CSV that understands
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file://filename entries.
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-U::
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--hide-unresolved::
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Only display entries resolved to a symbol.
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-s::
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--sort=::
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Sort by key(s): pid, comm, dso, symbol, parent.
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-p::
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--parent=<regex>::
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regex filter to identify parent, see: '--sort parent'
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-x::
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--exclude-other::
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Only display entries with parent-match.
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-w::
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--column-widths=<width[,width...]>::
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Force each column width to the provided list, for large terminal
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readability.
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-t::
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--field-separator=::
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Use a special separator character and don't pad with spaces, replacing
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all occurrences of this separator in symbol names (and other output)
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with a '.' character, that thus it's the only non valid separator.
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-D::
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--dump-raw-trace::
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Dump raw trace in ASCII.
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-g [type,min[,limit],order]::
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--call-graph::
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Display call chains using type, min percent threshold, optional print
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limit and order.
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type can be either:
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- flat: single column, linear exposure of call chains.
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- graph: use a graph tree, displaying absolute overhead rates.
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- fractal: like graph, but displays relative rates. Each branch of
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the tree is considered as a new profiled object. +
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order can be either:
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- callee: callee based call graph.
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- caller: inverted caller based call graph.
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Default: fractal,0.5,callee.
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-G::
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--inverted::
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alias for inverted caller based call graph.
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--pretty=<key>::
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Pretty printing style. key: normal, raw
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--stdio:: Use the stdio interface.
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--tui:: Use the TUI interface, that is integrated with annotate and allows
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zooming into DSOs or threads, among other features. Use of --tui
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requires a tty, if one is not present, as when piping to other
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commands, the stdio interface is used.
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-k::
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--vmlinux=<file>::
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vmlinux pathname
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--kallsyms=<file>::
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kallsyms pathname
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-m::
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--modules::
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Load module symbols. WARNING: This should only be used with -k and
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a LIVE kernel.
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-f::
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--force::
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Don't complain, do it.
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--symfs=<directory>::
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Look for files with symbols relative to this directory.
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-C::
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--cpu:: Only report samples for the list of CPUs provided. Multiple CPUs can
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be provided as a comma-separated list with no space: 0,1. Ranges of
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CPUs are specified with -: 0-2. Default is to report samples on all
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CPUs.
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-M::
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--disassembler-style=:: Set disassembler style for objdump.
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--source::
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Interleave source code with assembly code. Enabled by default,
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disable with --no-source.
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--asm-raw::
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Show raw instruction encoding of assembly instructions.
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--show-total-period:: Show a column with the sum of periods.
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-I::
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--show-info::
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Display extended information about the perf.data file. This adds
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information which may be very large and thus may clutter the display.
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It currently includes: cpu and numa topology of the host system.
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-b::
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--branch-stack::
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Use the addresses of sampled taken branches instead of the instruction
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address to build the histograms. To generate meaningful output, the
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perf.data file must have been obtained using perf record -b xxx where
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xxx is a branch filter option.
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SEE ALSO
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--------
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linkperf:perf-stat[1], linkperf:perf-annotate[1]
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