Re: Toggle perf stat on/off periodically and keep each sample

[Namhyung Kim <namhyung@kernel.org>]

Hello,

On Wed, Oct 16, 2024 at 09:28:33AM +0800, Fengkai Sun wrote:
> Hi all,
> 
> I've been using control fd and delay=-1 to toggle perf stat on until a
> certain point of the program, and it works like a charm.
> 
> Now, I want to do this periodically and keep all the results.
> Specifically, I have a performance-critical network program that reads
> the packets in batches and processes them, and I want to record the
> hardware counters on each batch, for future comparison.
> 
> Intuitively, this requires two functionalities I have no idea how to achieve:
> 
> 1. The ability to zero out all recorded counters when the current
> sample is finished and
> 2. The ability to keep individual samples, instead of outputting a
> single overall result when the process finishes.
> 
> I'm wondering if this can be achieved under current version of perf,
> and if such recording makes sense (e.g., does not incur too much
> overhead). Thank you!

I think you are looking for something like interval mode like -I 1000.

  $ sudo perf stat -a -I 1000 -e cycles,instructions sleep 5
  #           time             counts unit events
       1.001064439        644,313,943      cycles                                                                
       1.001064439        548,175,426      instructions                     #    0.85  insn per cycle            
       2.002682133        570,454,723      cycles                                                                
       2.002682133        426,891,566      instructions                     #    0.75  insn per cycle            
       3.004412672        565,162,161      cycles                                                                
       3.004412672        351,875,655      instructions                     #    0.62  insn per cycle            
       4.006131920        463,748,461      cycles                                                                
       4.006131920        239,702,866      instructions                     #    0.52  insn per cycle            
       5.001878221        466,409,911      cycles                                                                
       5.001878221        235,684,130      instructions                     #    0.51  insn per cycle

Of course it doesn't turn the events on and off.  But is it something
similar to what you want?

Thanks,
Namhyung