Perf

Profiling with Perf

The kernel comes with a performance analysis tool called perf that can be used to find the performance bottlenecks of a program.

Installation

   sudo apt-get install linux-tools-generic

Record information

## Profile system as long as needed, can be cancelled with Ctrl-C  
perf record -a -g

## Profile system for a given period of time  
perf record -a -g -s sleep $TIME_IN_SECONDS

## For the duration of a command  
perf record -a -g -s -- $COMMAND

Different things can be recorded:

-a to profile the whole system
-p $PID to profile only the given PID
-u $USER to profile only the given user

Reports are saved by default in $HOME/perf.data. Old reports are renamed as $HOME/perf.data.old.

Viewing the records

## View profile recorded
perf report -n

## With a graph
perf report -g

Other use cases

## Real-time measurement is done by perf top, like system-wide profiling  
perf top

## Profiling without accumulating stats
perf top -z

Perf Configuration

Use this file /proc/sys/kernel/perf_event_paranoid to restrict access to the performance counters.

 2, allow only user-space measurements
 1, allow both kernel and user measurements (default)
 0, allow access to CPU-specific data
-1, no paranoid at all