Commit 1a658771 authored by Liam R. Howlett's avatar Liam R. Howlett Committed by Greg Kroah-Hartman

sparc/ftrace: Fix ftrace graph time measurement


[ Upstream commit 48078d2d ]

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 722b3c74
("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: default avatarLiam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 45ceb845
......@@ -130,17 +130,16 @@ unsigned long prepare_ftrace_return(unsigned long parent,
if (unlikely(atomic_read(&current->tracing_graph_pause)))
return parent + 8UL;
if (ftrace_push_return_trace(parent, self_addr, &trace.depth,
frame_pointer, NULL) == -EBUSY)
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)) {
current->curr_ret_stack--;
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;
}
return return_hooker;
}
......
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