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    • Daniel Bristot de Oliveira's avatar
      tools/rtla: Add -U/--user-load option to timerlat · a23c05fd
      Daniel Bristot de Oliveira authored
      The timerlat tracer provides an interface for any application to wait
      for the timerlat's periodic wakeup. Currently, rtla timerlat uses it
      to dispatch its user-space workload (-u option).
      
      But as the tracer interface is generic, rtla timerlat can also be used
      to monitor any workload that uses it. For example, a user might
      place their own workload to wait on the tracer interface, and
      monitor the results with rtla timerlat.
      
      Add the -U option to rtla timerlat top and hist. With this option, rtla
      timerlat will not dispatch its workload but only setting up the
      system, waiting for a user to dispatch its workload.
      
      The sample code in this patch is an example of python application
      that loops in the timerlat tracer fd.
      
      To use it, dispatch:
      
       # rtla timerlat -U
      
      In a terminal, then run the python program on another terminal,
      specifying the CPU to run it. For example, setting on CPU 1:
      
       #./timerlat_load.py 1
      
      Then rtla timerlat will start printing the statistics of the
      ./timerlat_load.py app.
      
      An interesting point is that the "Ret user Timer Latency" value
      is the overall response time of the load. The sample load does
      a memory copy to exemplify that.
      
      The stop tracing options on rtla timerlat works in this setup
      as well, including auto analysis.
      
      Link: https://lkml.kernel.org/r/36e6bcf18fe15c7601048fd4c65aeb193c502cc8.1707229706.git.bristot@kernel.org
      
      
      
      Cc: Jonathan Corbet <corbet@lwn.net>
      Cc: Masami Hiramatsu <mhiramat@kernel.org>
      Signed-off-by: default avatarDaniel Bristot de Oliveira <bristot@kernel.org>
      a23c05fd
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