ability to use linux perf?

[anandijain]

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i have macos locally and i want to do some perf analysis. i was able to install linux-tools-generic and use perf but I get the following:

@anandijain ➜ ~/.../dev/JuliaBenchmarker/test/DiffEq (main ✗) $ perf stat ls
Error:
You may not have permission to collect stats.

Consider tweaking /proc/sys/kernel/perf_event_paranoid,
which controls use of the performance events system by
unprivileged users (without CAP_SYS_ADMIN).

The current value is 3:

  -1: Allow use of (almost) all events by all users
      Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
>= 0: Disallow ftrace function tracepoint by users without CAP_SYS_ADMIN
      Disallow raw tracepoint access by users without CAP_SYS_ADMIN
>= 1: Disallow CPU event access by users without CAP_SYS_ADMIN
>= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN

To make this setting permanent, edit /etc/sysctl.conf too, e.g.:

        kernel.perf_event_paranoid = -1

if i run it with sudo i get:

@anandijain ➜ ~/.../dev/JuliaBenchmarker/test/DiffEq (main ✗) $ sudo perf stat ls
bin.jl  Manifest.toml  perf.data  Project.toml  src

 Performance counter stats for 'ls':

              0.94 msec task-clock                #    0.659 CPUs utilized          
                 0      context-switches          #    0.000 K/sec                  
                 0      cpu-migrations            #    0.000 K/sec                  
                99      page-faults               #    0.106 M/sec                  
   <not supported>      cycles                                                      
   <not supported>      instructions                                                
   <not supported>      branches                                                    
   <not supported>      branch-misses                                               

       0.001423496 seconds time elapsed

       0.001459000 seconds user
       0.000000000 seconds sys

which isn't very helpful, since what I actually plan to analyze is instruction count.

i tried editing /proc/sys/kernel/perf_event_paranoid and /etc/sysctl.conf but it seems like i'm not allowed to edit these.

does anyone know how I could use codespaces to benchmark and record perf data?
thanks!

[samruddhikhandale]

Hi 👋

Have you tried updating /proc/sys/kernel/perf_event_paranoid with sudo sh -c 'echo 1 >/proc/sys/kernel/perf_event_paranoid' ?

You could also try sudo sysctl -w kernel.perf_event_paranoid=1 if the earlier command fails.

[YikChingTsui]

The OP said they're not allowed to do that. Here's what I get:

$ sudo sh -c 'echo 1 >/proc/sys/kernel/perf_event_paranoid'
sh: 1: cannot create /proc/sys/kernel/perf_event_paranoid: Read-only file system
$ sudo sysctl -w kernel.perf_event_paranoid=1
sysctl: setting key "kernel.perf_event_paranoid", ignoring: Read-only file system

[GitMensch]

Using the default codespace setup (has Ubunut focal) and apt install linux-tools i get

perf stat true
WARNING: perf not found for kernel 6.2.0-1016

  You may need to install the following packages for this specific kernel:
    linux-tools-6.2.0-1016-azure
    linux-cloud-tools-6.2.0-1016-azure

  You may also want to install one of the following packages to keep up to date:
    linux-tools-azure
    linux-cloud-tools-azure

but the later has no version for that kernel:

apt info linux-tools-azure
Package: linux-tools-azure
Version: 5.15.0.1051.59~20.04.40
Priority: optional
Section: metapackages
Source: linux-meta-azure-5.15
Origin: Ubuntu
Maintainer: Ubuntu Kernel Team <kernel-team@lists.ubuntu.com>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 10.2 kB
Depends: linux-tools-5.15.0-1051-azure
Download-Size: 2376 B
APT-Manual-Installed: yes
APT-Sources: http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
Description: Linux kernel versioned tools for Azure systems.

Is this expected? I guess there is a source repository missing in the default configuration that has the necessary kernel version...

[saagarjha]

These are in Jammy, but GitHub Codespaces ships with focal. While a terrible hack, I don't really care much about my codespaces so I just updated with do-release-upgrade and then installed what I needed.

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