table of contents
other versions
- jessie-backports 4.4-4~bpo8+1
PERF_4.4-TOP(1) | perf Manual | PERF_4.4-TOP(1) |
NAME¶
perf-top - System profiling tool.SYNOPSIS¶
perf top [-e <EVENT> | --event=EVENT] [<options>]
DESCRIPTION¶
This command generates and displays a performance counter profile in real time.OPTIONS¶
-a, --all-cpusSystem-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.
-F <freq>, --freq=<freq>
Profile at this frequency.
-i, --inherit
Child tasks do not inherit counters.
-k <path>, --vmlinux=<path>
Path to vmlinux. Required for annotation
functionality.
-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).
-n, --show-nr-samples
By default, every sort keys not specified in --field will be appended automatically.
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.
--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.
--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.
--ignore-callees=<regex>
Default: 127
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).
-w, --column-widths=<width[,width...]>
"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.
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.
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.
[z]
Toggle event count zeroing across display updates.
[qQ]
Quit.
Pressing any unmapped key displays a menu, and prompts for input.
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..ft C void foo(void) { /* do something */ } void bar(void) { /* do something */ foo(); } int main(void) { bar() return 0; } .ft
.ft C Overhead Symbol ........ ..................... 60.00% foo | --- foo bar main __libc_start_main 40.00% bar | --- bar main __libc_start_main .ft
.ft C 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 .ft
SEE ALSO¶
perf_4.4-stat(1), perf_4.4-list(1), perf_4.4-report(1)2016-03-20 | perf |