How to Install perf Tool on CentOS and Ubuntu

Perf is a performance counter for Linux. With it you can know many secrets of the running linux system. For example why L2 cache misses are happening. Why your disk is showing activity, which code paths are making the stalls in the kernel, and many other things. In this article, we will show basics of perf and how you can use it to get some data about performance of your system.

How to Install perf

Installing perf userpace tools via termial (along with awk) is straightforward.

On Ubuntu type

sudo apt install linux-tools-common gawk

On CentOS and Fedora

sudo yum install perf gawk

Few usage of perf tool

Lets record disk i/o using the below command.

sudo perf record -e block:block_rq_issue -ag

It will record data, you can press ctrl-c to stop it after couple of seconds. Then issue following command

sudo perf report

And you will get something like this:

perf report
expanded report

The plus means that report is expandable and you can see which code paths are responsible. I expanded one line in second image, there we see more info.

Lets next check cache misses. This command will record cpu level 1 data cache misses

sudo perf record -e L1-dcache-load-misses -c 10000 -ag -- sleep 5

So when we check report with sudo perf report -f we will see which code is responsible for the misses

Skype causing cache misses

We see that Skype's function is responsible for 0.83% of cache misses in L1 Data cache.

So far we recorded and then analyzed the record, but what if you want it real time, to record and see output immediately? Read on, in next section we cover that.

Real-Time Scripts

Perf is very powerful tool, but not at the same time not the best documented tool due to frequent changes to underlying framework. So for easier performance counting in real time, we will use a suite of scripts from github. Lets clone them


git clone --depth 1

cd perf-tools

And you are all set. Now we run some scripts:

sudo ./iolatency

iolatency, disk latency data

This script will give us latency of the disk as histogram. I have run it just for a second, you can have it run longer. I don't want because I have 5400 rpm HDD, and results just cant be good, so why run it.

Lets try some more scripts.

sudo ./fs/cachestat


This script uses perf to get cache misses every second and prints it to a line. Notice that first 3 seconds there were no misses, an latter they started. That is because I started rebuild of my project in Android Studio just at that time. I can say that Intel made pretty good branch predictor in Haswell. Cache hit percentage rarely drops bellow 95% on my i7 with 6 mb of L3 cache.

 sudo ./kernel/funccount -t 5 -d 5 'ext4*'
Tracing "ext4*" for 5 seconds. Top 5 only...

ext4_mark_iloc_dirty 109
ext4_reserve_inode_write 109
ext4_get_group_desc 112
ext4_inode_table 112
ext4_journal_check_start 155

This script traces kernel function you type (ext4 in this example) for amount of time you type ( -d 5 sec here) and outputs top list with as many spots you set (-t 5 here).

Some non-realtime scripts

This script uses perf_events to count syscalls :

sudo ./syscount -c
Tracing... Ctrl-C to end.
^Csleep: Interrupt
exit 1
lseek 1
newuname 1
dup 2
sched_getaffinity 2
tgkill 2
timerfd_settime 2
unlink 2
access 3
prctl 3
set_robust_list 4
fdatasync 5
getsockopt 5
epoll_ctl 6
newlstat 6
ftruncate 7
munmap 8
shutdown 8
inotify_add_watch 9
bind 10
mmap 14

It is not real time like above one above, you have to press ctrl-C to stop counting and then you get output.

If you want to track call of specific process you first need to get its PID with command

sudo ./syscount -v

and then need to use pid number like this

./syscount -cp 5656

to see which syscalls a process with pid 5656 calls the most.


We have gone through basic examples of what can be done with perf to gauge performance data of your system. But we only scratched the surface, as perf is really extensive tool and you can use it to get many details. Unfortunately we can only go so much in one article. Thank you for reading and good day.


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Comments (2)

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  1. Thubo says:

    Thanks for the nice intro.

    One litte note:
    Most users will want to install the linux-tools-generic package instead of the linux-tools-common package.

    The generic package is an meta-package which contains everything required to run perf for the current kernel.
    If you are running an older kernel you need linux-tools-`uname -r`, which installs the 'older' linux tools.

    • Mihajlo Milenovic says:

      Thank you for insightful reply. I have ran the tools on Fedora as that is what I was using at the time, only install was done in Ubntu and CentOS VMs for reference for other users. Now switched to ubuntu, will try linux-tools-generic.

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