* [PATCH] sparc/ftrace: Fix ftrace graph time measurement
@ 2017-05-17 15:47 Liam R. Howlett
2017-05-17 19:09 ` David Miller
0 siblings, 1 reply; 2+ messages in thread
From: Liam R. Howlett @ 2017-05-17 15:47 UTC (permalink / raw)
To: sparclinux
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 722b3c746953
("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>
---
arch/sparc/kernel/ftrace.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/arch/sparc/kernel/ftrace.c b/arch/sparc/kernel/ftrace.c
index 6bcff69..cec54dc 100644
--- a/arch/sparc/kernel/ftrace.c
+++ b/arch/sparc/kernel/ftrace.c
@@ -130,17 +130,16 @@ unsigned long prepare_ftrace_return(unsigned long parent,
if (unlikely(atomic_read(¤t->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;
}
--
2.1.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] sparc/ftrace: Fix ftrace graph time measurement
2017-05-17 15:47 [PATCH] sparc/ftrace: Fix ftrace graph time measurement Liam R. Howlett
@ 2017-05-17 19:09 ` David Miller
0 siblings, 0 replies; 2+ messages in thread
From: David Miller @ 2017-05-17 19:09 UTC (permalink / raw)
To: sparclinux
From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
Date: Wed, 17 May 2017 11:47:00 -0400
> 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 722b3c746953
> ("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>
Applied, thanks.
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