2009-10-07 23:26:51

by Christoph Lameter

Subject: [Patch vs. percpu next] Use this_cpu_xx for ftrace

From: Christoph Lameter <[email protected]>
Subject: tracing: Use this_cpu_xx for ftrace

this_cpu_xx can reduce the instruction count here and also
avoid address arithmetic.

Signed-off-by: Christoph Lameter <[email protected]>


---
kernel/trace/trace.c | 8 ++++----
kernel/trace/trace.h | 2 +-
2 files changed, 5 insertions(+), 5 deletions(-)

Index: linux-2.6/kernel/trace/trace.c
===================================================================
--- linux-2.6.orig/kernel/trace/trace.c 2009-10-07 18:07:48.000000000 -0500
+++ linux-2.6/kernel/trace/trace.c 2009-10-07 18:09:42.000000000 -0500
@@ -86,17 +86,17 @@ static int dummy_set_flag(u32 old_flags,
*/
static int tracing_disabled = 1;

-DEFINE_PER_CPU(local_t, ftrace_cpu_disabled);
+DEFINE_PER_CPU(int, ftrace_cpu_disabled);

static inline void ftrace_disable_cpu(void)
{
preempt_disable();
- local_inc(&__get_cpu_var(ftrace_cpu_disabled));
+ __this_cpu_inc(per_cpu_var(ftrace_cpu_disabled));
}

static inline void ftrace_enable_cpu(void)
{
- local_dec(&__get_cpu_var(ftrace_cpu_disabled));
+ __this_cpu_dec(per_cpu_var(ftrace_cpu_disabled));
preempt_enable();
}

@@ -1085,7 +1085,7 @@ trace_function(struct trace_array *tr,
struct ftrace_entry *entry;

/* If we are reading the ring buffer, don't trace */
- if (unlikely(local_read(&__get_cpu_var(ftrace_cpu_disabled))))
+ if (unlikely(__this_cpu_read(per_cpu_var(ftrace_cpu_disabled))))
return;

event = trace_buffer_lock_reserve(buffer, TRACE_FN, sizeof(*entry),
Index: linux-2.6/kernel/trace/trace.h
===================================================================
--- linux-2.6.orig/kernel/trace/trace.h 2009-10-07 18:08:59.000000000 -0500
+++ linux-2.6/kernel/trace/trace.h 2009-10-07 18:09:19.000000000 -0500
@@ -413,7 +413,7 @@ extern int DYN_FTRACE_TEST_NAME(void);

extern int ring_buffer_expanded;
extern bool tracing_selftest_disabled;
-DECLARE_PER_CPU(local_t, ftrace_cpu_disabled);
+DECLARE_PER_CPU(int, ftrace_cpu_disabled);

#ifdef CONFIG_FTRACE_STARTUP_TEST
extern int trace_selftest_startup_function(struct tracer *trace,

2009-10-11 08:25:29

by Ingo Molnar

Subject: Re: [Patch vs. percpu next] Use this_cpu_xx for ftrace

* Christoph Lameter <[email protected]> wrote:

> From: Christoph Lameter <[email protected]>
> Subject: tracing: Use this_cpu_xx for ftrace
>
> this_cpu_xx can reduce the instruction count here and also
> avoid address arithmetic.
>
> Signed-off-by: Christoph Lameter <[email protected]>

Acked-by: Ingo Molnar <[email protected]>

Thanks Christoph,

Ingo

2009-10-12 10:53:44

by Tejun Heo

Subject: Re: [Patch vs. percpu next] Use this_cpu_xx for ftrace

Christoph Lameter wrote:
> From: Christoph Lameter <[email protected]>
> Subject: tracing: Use this_cpu_xx for ftrace
>
> this_cpu_xx can reduce the instruction count here and also
> avoid address arithmetic.
>
> Signed-off-by: Christoph Lameter <[email protected]>

applied to percpu#for-next. Thanks.

--
tejun