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

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> On Jul 27, 2016, at 8:53 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
> 
> I'm thinking you only need one tracepoint, and use function_graph
> tracer for the length of the function call.
> 
> # cd /sys/kernel/debug/tracing
> # echo __alloc_pages_nodemask > set_ftrace_filter
> # echo function_graph > current_tracer
> # echo 1 > events/kmem/trace_mm_slowpath/enable

Thank you so much for your feedback! 

Actually, the goal is to only single out those cases with latencies higher than a given
threshold.

So, in accordance with this, I added those begin/end tracepoints and thought I 
could use a script to read the output of trace_pipe and only write to disk the trace 
information associated with latencies above the threshold. This would help prevent 
high disk I/O, especially when the threshold set is high.

I looked at function graph trace, as you’d suggested. I saw that I could set a threshold 
there using tracing_thresh. But the problem was that slowpath trace information was printed
for all the cases (even when __alloc_pages_nodemask latencies were below the threshold).
Is there a way to print tracepoint information only when __alloc_pages_nodemask
exceeds the threshold?

Thanks!

Janani.
> 
> -- Steve
> 
> 
>> 	return page;
>> }
>> 
> 

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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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