I am working on my computer, trying to write some device code. I checked into dmesg to get some info, and saw this:

perf interrupt took too long (2507 > 2500), lowering kernel.perf_event_max_sample_rate to 50000

what does this event mean? Cause? Concern?


This should not be a concern.perf is a tool to handle CPU performance. The kernal is capable of automatically determining the sample rate without affecting the performance of system. Here is a thread on this from the Arch forum.

  • 2
    would it make a difference if I switch to another clock source like the HPET? – Janus Troelsen Sep 11 '15 at 16:48

This answer from the Arch Forum sums it up:

This message is informational and nothing to worry about.

It has to do with the Linux perf tool which is included in the kernel. The kernel automagically determines the sample rate that could be used without impacting system performance too much; and it logs this even when perf isn't active, or even installed.

Messages like this are triggered by high(er) system load or a cpu that is scaling.

  • 5
    I got this after doing I/O benchmarking combined with repated sync. Nothing to worry about as long as numbers after interrupt took too long (3979 > 3930) are close enough. If the bigger one is say 10x the another then you may have some problems with CPU scheduling. – Mikko Rantalainen Dec 16 '17 at 13:58

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