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sparc/ftrace: Fix ftrace graph time measurement 

The ftrace function_graph time measurements of a given function is not
accurate according to those recorded by ftrace using the function
filters.  This change pulls the x86_64 fix from 'commit 722b3c7469
("ftrace/graph: Trace function entry before updating index")' into the
sparc specific prepare_ftrace_return which stops ftrace from
counting interrupted tasks in the time measurement.

Example measurements for select_task_rq_fair running "hackbench 100
process 1000":

              |  tracing/trace_stat/function0  |  function_graph
 Before patch |  2.802 us                      |  4.255 us
 After patch  |  2.749 us                      |  3.094 us

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Liam R. Howlett 2017-05-17 11:47:00 -04:00 committed by David S. Miller
parent deba804c90
commit 48078d2dac
1 changed files with 7 additions and 8 deletions
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15
arch/sparc/kernel/ftrace.c
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@ -130,18 +130,17 @@ unsigned long prepare_ftrace_return(unsigned long parent,
if (unlikely(atomic_read(&current->tracing_graph_pause)))
return parent + 8UL;
trace.func = self_addr;
trace.depth = current->curr_ret_stack + 1;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace))
return parent + 8UL;
if (ftrace_push_return_trace(parent, self_addr, &trace.depth,
frame_pointer, NULL) == -EBUSY)
return parent + 8UL;
trace.func = self_addr;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace)) {
current->curr_ret_stack--;
return parent + 8UL;
}
return return_hooker;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */