How to Use OProfile
Table of Contents
OProfile is a system-wide profiler for Linux systems, capable of profiling all running code at low overhead.
Operf vs Opcontrol
Legacy OProfile consists of the opcontrol shell script for configuring, starting, and stopping a profiling session. To this purpose, a kernel driver is used for collecting samples, which are recorded into sample files. A disadvantage of this mode is the necessity of elevated user privileges to run opcontrol. opcontrol was discontinued in version 1.0.0.
Operf was designed to be used in place of opcontrol for profiling. It uses the Linux Performance Events Subsystem, and therefore, does not require the use of the opcontrol daemon or any elevated privileges. The use of operf and opcontrol are mutually exclusive. operf was introduced in version 0.9.8.
operf requires hardware support for profiling. In the case of an ARM processor, the Performance Monitoring Unit (PMU) and arm-pmu driver must be present. On devices without hardware support, oprofile version 0.9.9 and opcontrol must be used. Without hardware support, operf will report
Your kernel's Performance Events Subsystem does not support your processor type
Prerequisites
- Kernel built with the following options:
CONFIG_PROFILING=yCONFIG_OPROFILE=y
- Target RFS containing:
oprofile- Native toolchain required if profiling the kernel
- Uncompressed kernel image within the RFS if profiling the kernel.
- You can include this in your Factory build by running make menuconfig and selecting Target Software > Kernel > Include uncompressed kernel image within the RFS
bash- A number of utilities, which are typically provided by
busyboxor the following packagescoreutilswhichmktempprocps
- In order to profile the libraries, unstripped versions need to be included in root filesystem.
Run make menuconfig and unselect: Target Configuration > Build RFS > Strip all libraries and binaries in the RFS
And then run:- make rfs-distclean
- make
If you are using Factory on your desktop, then you can run "make checktool-oprofile" to check your platform for compatibility with OProfile.
Procedure: opcontrol-based oprofile
Initialization
If you want to profile the kernel you must copy the uncompressed vmlinux file from the root of your kernel source tree to your RFS. If your distribution comes from the Timesys Web Factory then you will have to rebuild your kernel from source, as this file is not included in the binary installer. You must have a native toolchain installed on the target in order to profile the kernel. Then you can initialize OProfile by entering the following on the target:
opcontrol --vmlinux=/path/to/vmlinux/file
If you don't want to profile the kernel, you can initialize by entering the following on the target:
opcontrol --no-vmlinux
Profiling
To begin profiling, enter the following on the target:
opcontrol --start
Then perform any action and run any software you wish to profile. When finished enter the following on the target:
opcontrol --shutdown
Reporting
To obtain a summary of the profiling information enter the following on the target:
opreport
For a more detailed summary enter the following on the target:
opreport -l
Examples
Here is an example session profiling the kernel on an OMAP 3530 board:
# opcontrol --vmlinux=/boot/vmlinux
# opcontrol --start
Using 2.6+ OProfile kernel interface.
Reading module info.
Using log file /var/lib/oprofile/samples/oprofiled.log
Daemon started.
Profiler running.
# cat vmlinux > /dev/null
# opcontrol --shutdown
Detected stale lock file. Removing.
# opreport
CPU: CPU with timer interrupt, speed 0 MHz (estimated)
Profiling through timer interrupt
TIMER:0|
samples| %|
------------------
5717 99.8603 vmlinux
4 0.0699 libc-2.7.so
2 0.0349 busybox
2 0.0349 ld-2.7.so
Procedure: operf-based oprofile
Profiling
To profile your application:
operf application [ application_args ]
Reporting
To obtain a summary of the profiling information enter the following on the target:
opreport
For a more detailed summary enter the following on the target:
opreport -l
Example
Here is an example session profiling the kernel on an i.MX6 board:
# cp /bin/busybox .
# operf --vmlinux=/boot/vmlinux ./busybox --help
BusyBox v1.20.2 (2014-09-25 16:48:10 EDT) multi-call binary.
Copyright (C) 1998-2011 Erik Andersen, Rob Landley, Denys Vlasenko
and others. Licensed under GPLv2.
See source distribution for full notice.
...
whois, xargs, xz, xzcat, yes, zcat, zcip
operf: Profiler started
Profiling done.
#
# opreport -l ./busybox
Using //oprofile_data/samples/ for samples directory.
CPU: ARM Cortex-A9, speed 996000 MHz (estimated)
Counted CPU_CYCLES events (CPU cycle) with a unit mask of 0x00 (No unit mask) count 100000
samples % image name symbol name
34 51.5152 vmlinux _raw_spin_unlock_irqrestore
3 4.5455 vmlinux do_page_fault
2 3.0303 ld-2.17.so _dl_relocate_object
2 3.0303 vmlinux fget_light
2 3.0303 vmlinux vector_swi
1 1.5152 busybox /busybox^M
1 1.5152 ld-2.17.so _dl_check_map_versions
1 1.5152 ld-2.17.so _dl_init_paths
1 1.5152 libc-2.17.so _dl_addr
1 1.5152 libc-2.17.so mallopt
1 1.5152 vmlinux __remove_shared_vm_struct
1 1.5152 vmlinux __slab_free.isra.44
1 1.5152 vmlinux __srcu_read_lock
1 1.5152 vmlinux _set_bit
1 1.5152 vmlinux copy_page
1 1.5152 vmlinux do_get_write_access
1 1.5152 vmlinux do_sync_read
1 1.5152 vmlinux find_get_page
1 1.5152 vmlinux find_vma
1 1.5152 vmlinux getname_flags
1 1.5152 vmlinux mutex_lock
1 1.5152 vmlinux n_tty_write
1 1.5152 vmlinux release_pages
1 1.5152 vmlinux tty_write_unlock
1 1.5152 vmlinux uart_start
1 1.5152 vmlinux unmap_single_vma
1 1.5152 vmlinux v7_flush_kern_dcache_area
1 1.5152 vmlinux vfs_write
Additional Resources
- OProfile Getting Started Guide - Official OProfile tutorial
- OProfile - Official OProfile website
