sparc/ftrace: Fix ftrace graph time measurement

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[ Upstream commit 48078d2dac ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Liam R. Howlett 2017-05-17 11:47:00 -04:00 • committed by Greg Kroah-Hartman

parent 45ceb845ef

commit 1a658771d5

1 changed files with 6 additions and 7 deletions

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arch/sparc/kernel/ftrace.c

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