Measuring performance with the perf kernel tool
top on Steroids
You can create a performance counter profile in real time with perf top
(Figure 1). The overview is similar to that of top
, but you can jump directly to the individual events.

perf stat
counts the events of the entire system until you abort by pressing Ctrl+C, or the specified command terminates. Listing 3 shows the subcommand in action; it lists two events for the factor
command.
Listing 3
Output from perf stat
01 $ sudo perf stat -e branches -e branch-misses factor 120808125801214124898080833 02 120808125801214124898080833: 13 29 911 7589 21089 77471 28369829 03 04 Performance counter stats for 'factor 120808125801214124898080833': 05 06 191,242 branches 07 10,332 branch-misses # 5.40% of all branches 08 09 0.000649438 seconds time elapsed 10 11 0.000699000 seconds user 12 0.000000000000 seconds sys
Data Recorder
The perf
record
command can generate a performance counter profile for a specific command. If you want an overview of the entire system, or if the process to be examined is unknown, simply add the sleep
command:
sudo perf record -ag sleep 5
This line creates the default perf.data
file in the current directory. The -a
switch ensures that perf
considers all CPUs, and -g
generates a call graph. -i
lets you feed a file to perf record
.
The perf report
command evaluates the stored data and uses the perf.data
file. As with perf top
, the command presents an overview. After pressing Enter, you also see details for the functions.
By the way, the --sort= comm,dso
switch (see Figure 1) provides a better overview. Figure 2 shows the output for an Intel Kaby Lake system with Gnome 3.30.1 playing a movie in Firefox 63.0.3. The figure shows that the CPU and not the GPU is used for decoding.
Event-Driven
If only certain events are of interest, the -e
switch can help. Listing 4 shows the output on a system with Rsync running.
Listing 4
Track Events
01 $ sudo perf report --stdio 02 [...] 03 # Samples: 1K of event 'block:block_rq_issue' 04 # Event count (approx.): 1741 05 # 06 # Children Self Command Shared Object Symbol 07 # ........ .... ........... ................ .................... 08 # 09 93.74% 93.74% rsync kernel.kallsyms] [k] blk_peek_request 10 | 11 |--89.20%-- __lxstat64 12 | blk_peek_request 13 | 14 |--3.45%-- __GI___mkdir 15 | blk_peek_request 16 | 17 |--0.63%-- 0x646c6975622f3930 18 | __GI___link 19 | blk_peek_request 20 | 21 -0.46%-- 0x6d492f636f642f65 22 __GI___link 23 blk_peek_request 24 25 89.20% 0.00% rsync libc-2.27.so [.] __lxstat64 26 | 27 ---__lxstat64 28 blk_peek_request 29 [...]
--stdio
tells perf
to display the overview in plain text directly on the console. The recorded event was a request to the kernel block layer. The command line was:
sudo perf record -e block:block_rq_issue -ag
« Previous 1 2 3 4 Next »
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Direct Download
Read full article as PDF:
Price $2.95
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you've found an article to be beneficial.
News
-
Linux Mint Finally Receiving Support for Gestures
If you use the Linux Mint Cinnamon desktop, you'll be thrilled to know that 21.2 is getting support for gestures on touchscreen devices and touchpads.
-
An All-Snap Version of Ubuntu is In The Works
Along with the standard deb version of the open-source operating system, Canonical will release an-all snap version.
-
Mageia 9 Beta 2 Ready for Testing
The latest beta of the popular Mageia distribution now includes the latest kernel and plenty of updated applications.
-
KDE Plasma 6 Looks to Bring Basic HDR Support
The KWin piece of KDE Plasma now has HDR support and color management geared for the 6.0 release.
-
Bodhi Linux 7.0 Beta Ready for Testing
The latest iteration of the Bohdi Linux distribution is now available for those who want to experience what's in store and for testing purposes.
-
Changes Coming to Ubuntu PPA Usage
The way you manage Personal Package Archives will be changing with the release of Ubuntu 23.10.
-
AlmaLinux 9.2 Now Available for Download
AlmaLinux has been released and provides a free alternative to upstream Red Hat Enterprise Linux.
-
An Immutable Version of Fedora Is Under Consideration
For anyone who's a fan of using immutable versions of Linux, the Fedora team is currently considering adding a new spin called Fedora Onyx.
-
New Release of Br OS Includes ChatGPT Integration
Br OS 23.04 is now available and is geared specifically toward web content creation.
-
Command-Line Only Peropesis 2.1 Available Now
The latest iteration of Peropesis has been released with plenty of updates and introduces new software development tools.