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Do I need to have to run perf userspace tool as system administrator (root), or can I run it (or at least some subcommands) as an ordinary user?

Gilles 'SO- stop being evil'
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Jakub Narębski
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    Unix programs that can't do what they need to do for lack of permissions will usually thrown an error if they can't do their job. Run it and see! – Caleb Jun 02 '11 at 10:55
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    I am asking this question to decide whether it is worth trying to install (as ordinary user, in $HOME) userspace part of **`perf`** tool (which is/can be non-trivial). – Jakub Narębski Jun 02 '11 at 12:19
  • FYI in Ubuntu **`perf`** is in `linux-tools` package, so installing `perf` there is simple. – Jakub Narębski Jun 12 '13 at 16:59
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    @JakubNarębski: Except if it is not your own machine and the admins are reluctant to install packages. – Martin Ueding May 15 '19 at 12:09

1 Answers1

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What you can do with perf without being root depends on the kernel.perf_event_paranoid sysctl setting.

  • kernel.perf_event_paranoid = 2: you can't take any measurements. The perf utility might still be useful to analyse existing records with perf ls, perf report, perf timechart or perf trace.
  • kernel.perf_event_paranoid = 1: you can trace a command with perf stat or perf record, and get kernel profiling data.
  • kernel.perf_event_paranoid = 0: you can trace a command with perf stat or perf record, and get CPU event data.
  • kernel.perf_event_paranoid = -1: you get raw access to kernel tracepoints (specifically, you can mmap the file created by perf_event_open, I don't know what the implications are).
pevik
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Gilles 'SO- stop being evil'
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    Nice. `cat /proc/sys/kernel/perf_event_paranoid` returns 1, so it seems that I would be able to take at least some measurements (BTW. whats the difference betwen "kernel profiling data" and "CPU event data"? Reference is enough) – Jakub Narębski Jun 02 '11 at 17:48
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    @Jakub: From what I understand, kernel events let you see calls to various kernel functions. CPU events are counters in the CPU that tell you how many times a particular location in memory was hit. I've never used them, so I can't tell you more about them; [LWN](http://www.google.com/search?q=perf-event+site:lwn.net) has quite a few article on the topic, and it's still evolving. – Gilles 'SO- stop being evil' Jun 02 '11 at 18:03
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    With paranoid=2, you can still profile your own code in user-space (e.g. `perf stat awk 'BEGIN{for(i=0;i<10000000;i++){}}'` will show accurate user-space cycle and instruction counts, and you can even get counts for `uops_issued.any` and so on), but you don't get counts for code that ran during system calls/interrupts. So the reported CPU frequency (cycles / time) is at least slightly lower than actual because of time spent in kernel. See also [What restriction is perf\_event\_paranoid == 1 actually putting on x86 perf?](https://stackoverflow.com/q/51911368) – Peter Cordes Aug 19 '18 at 20:58
  • "CPU events" means profiling everything on a whole core, instead of per-process / thread. i.e. paranoid=1 or higher stops you from profiling other user's code, and 1 only lets you profile kernel code invoked by your own processes (system calls.) – Peter Cordes Aug 19 '18 at 21:00