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Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath

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> On Aug 5, 2016, at 10:00 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
> 
>> 
> 
> You probably want to clear the trace here, or set function_graph here
> first. Because the function graph starts writing to the buffer
> immediately.
> 

I did that, just didn’t include it here :)
>> 
> 
> When threshold is set, the entry is not recorded, because it is only
> showing the exit and the time it took in that function:
> 
> 0) kswapd0-52 | + 54.141 us | } /* shrink_zone */
> 
> shrink_zone() took 54.141us.
> 
> The reason it doesn't record the entry is because it would fill the
> entire buffer, if the threshold is never hit. One can't predict the
> time in a function when you first enter that function.

Right!
> 
>> 
> 
> You need your own interpreter here. Perhaps a module that either reads
> the tracepoints directly and registers a function graph tracer itself.
> The trace events and function tracers are plugable. You don't need to
> use the tracing system to use them. Just hook into them directly.
> 
> Things like the wakeup latency tracer does this. Look at
> kernel/trace/trace_sched_wakeup.c for an example. It hooks into the
> sched_wakeup and sched_switch tracepoints, and also has a way to use
> function and function_graph tracing.
> 
> 

I will look at that file. Thanks!
> 
>> 
> 
> Great! And note, even if you add extra tracepoints, you can hook
> directly into them too. Again, see the trace_sched_wakeup.c for
> examples.

Alright. Thanks for all the help! :)

Janani.
> 
> -- Steve

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[PATCH 0/2] New tracepoints for slowpath and memory compaction Janani Ravichandran <janani.rvchndrn@gmail.com> - 2016-07-27 16:50 +0200
  [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Janani Ravichandran <janani.rvchndrn@gmail.com> - 2016-07-27 16:50 +0200
    Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Steven Rostedt <rostedt@goodmis.org> - 2016-07-27 17:30 +0200
      Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Dave Hansen <dave.hansen@intel.com> - 2016-07-27 19:30 +0200
        Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Steven Rostedt <rostedt@goodmis.org> - 2016-07-27 19:40 +0200
      Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Janani Ravichandran <janani.rvchndrn@gmail.com> - 2016-07-28 22:20 +0200
        Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Steven Rostedt <rostedt@goodmis.org> - 2016-08-04 17:30 +0200
          Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Janani Ravichandran <janani.rvchndrn@gmail.com> - 2016-08-05 18:20 +0200
            Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Steven Rostedt <rostedt@goodmis.org> - 2016-08-05 18:40 +0200
              Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Janani Ravichandran <janani.rvchndrn@gmail.com> - 2016-08-07 12:40 +0200
    Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Michal Hocko <mhocko@kernel.org> - 2016-07-27 18:40 +0200
      Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Rik van Riel <riel@surriel.com> - 2016-07-27 20:20 +0200
        Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Steven Rostedt <rostedt@goodmis.org> - 2016-07-27 20:30 +0200
        Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Michal Hocko <mhocko@kernel.org> - 2016-07-27 20:50 +0200
          Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Rik van Riel <riel@surriel.com> - 2016-07-27 21:00 +0200
  [PATCH 2/2] mm: compaction.c: Add/Modify direct compaction  tracepoints Janani Ravichandran <janani.rvchndrn@gmail.com> - 2016-07-27 17:00 +0200
    Re: [PATCH 2/2] mm: compaction.c: Add/Modify direct compaction  tracepoints Steven Rostedt <rostedt@goodmis.org> - 2016-07-27 17:30 +0200
    Re: [PATCH 2/2] mm: compaction.c: Add/Modify direct compaction  tracepoints Vlastimil Babka <vbabka@suse.cz> - 2016-08-01 15:30 +0200
      Re: [PATCH 2/2] mm: compaction.c: Add/Modify direct compaction tracepoints Janani Ravichandran <janani.rvchndrn@gmail.com> - 2016-08-07 14:40 +0200

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