linux-kernel - [tip:perf/core] perf: Remove useless atomic

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Message-ID: <tip-vw9lg588x1ic248whybjon0c@git.kernel.org>
Date:	Tue, 29 Oct 2013 07:07:58 -0700
From:	tip-bot for Peter Zijlstra <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	peterz@...radead.org, tglx@...utronix.de, dzickus@...hat.com
Subject: [tip:perf/core] perf: Remove useless atomic_t

Commit-ID:  d9494cb4299da66541a3f3ab82c552889bee0606
Gitweb:     http://git.kernel.org/tip/d9494cb4299da66541a3f3ab82c552889bee0606
Author:     Peter Zijlstra <peterz@...radead.org>
AuthorDate: Thu, 17 Oct 2013 15:36:19 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 29 Oct 2013 12:02:49 +0100

perf: Remove useless atomic_t

There's nothing atomic about atomic_set vs atomic_read; so remove the
atomic_t usage.

Also, make running_sample_length static as it really is (and should
be) local to this translation unit.

Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Cc: eranian@...gle.com
Cc: Don Zickus <dzickus@...hat.com>
Cc: jmario@...hat.com
Cc: acme@...radead.org
Cc: dave.hansen@...ux.intel.com
Link: http://lkml.kernel.org/n/tip-vw9lg588x1ic248whybjon0c@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/events/core.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5bd7fe4..028dad9 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -175,8 +175,8 @@ int sysctl_perf_event_sample_rate __read_mostly	= DEFAULT_MAX_SAMPLE_RATE;
 static int max_samples_per_tick __read_mostly	= DIV_ROUND_UP(DEFAULT_MAX_SAMPLE_RATE, HZ);
 static int perf_sample_period_ns __read_mostly	= DEFAULT_SAMPLE_PERIOD_NS;
 
-static atomic_t perf_sample_allowed_ns __read_mostly =
-	ATOMIC_INIT( DEFAULT_SAMPLE_PERIOD_NS * DEFAULT_CPU_TIME_MAX_PERCENT / 100);
+static int perf_sample_allowed_ns __read_mostly =
+	DEFAULT_SAMPLE_PERIOD_NS * DEFAULT_CPU_TIME_MAX_PERCENT / 100;
 
 void update_perf_cpu_limits(void)
 {
@@ -184,7 +184,7 @@ void update_perf_cpu_limits(void)
 
 	tmp *= sysctl_perf_cpu_time_max_percent;
 	do_div(tmp, 100);
-	atomic_set(&perf_sample_allowed_ns, tmp);
+	ACCESS_ONCE(perf_sample_allowed_ns) = tmp;
 }
 
 static int perf_rotate_context(struct perf_cpu_context *cpuctx);
@@ -228,14 +228,15 @@ int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write,
  * we detect that events are taking too long.
  */
 #define NR_ACCUMULATED_SAMPLES 128
-DEFINE_PER_CPU(u64, running_sample_length);
+static DEFINE_PER_CPU(u64, running_sample_length);
 
 void perf_sample_event_took(u64 sample_len_ns)
 {
 	u64 avg_local_sample_len;
 	u64 local_samples_len;
+	u64 allowed_ns = ACCESS_ONCE(perf_sample_allowed_ns);
 
-	if (atomic_read(&perf_sample_allowed_ns) == 0)
+	if (allowed_ns == 0)
 		return;
 
 	/* decay the counter by 1 average sample */
@@ -251,7 +252,7 @@ void perf_sample_event_took(u64 sample_len_ns)
 	 */
 	avg_local_sample_len = local_samples_len/NR_ACCUMULATED_SAMPLES;
 
-	if (avg_local_sample_len <= atomic_read(&perf_sample_allowed_ns))
+	if (avg_local_sample_len <= allowed_ns)
 		return;
 
 	if (max_samples_per_tick <= 1)
@@ -262,10 +263,9 @@ void perf_sample_event_took(u64 sample_len_ns)
 	perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;
 
 	printk_ratelimited(KERN_WARNING
-			"perf samples too long (%lld > %d), lowering "
+			"perf samples too long (%lld > %lld), lowering "
 			"kernel.perf_event_max_sample_rate to %d\n",
-			avg_local_sample_len,
-			atomic_read(&perf_sample_allowed_ns),
+			avg_local_sample_len, allowed_ns,
 			sysctl_perf_event_sample_rate);
 
 	update_perf_cpu_limits();
--
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