[PATCH 2/4] ring-buffer: only periodically call cond_resched to ring-buffer-benchmark

Steven Rostedt
2009-05-08T04:35:06Z

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From: Steven Rostedt <srostedt@redhat.com>

Calling cond_resched at every iteration of the loop adds a bit of
overhead to the benchmark.

This patch does two things.

1) only calls cond-resched when CONFIG_PREEMPT is not enabled
2) only calls cond-resched after so many traces has been performed.

[ Impact: less overhead to the ring-buffer-benchmark ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/ring_buffer_benchmark.c | 11 +++++++++--
1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index f4ceb45..a7c048b 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -218,16 +218,23 @@ static void ring_buffer_producer(void)
}
do_gettimeofday(&end_tv);

- if (consumer && !(++cnt % wakeup_interval))
+ cnt++;
+ if (consumer && !(cnt % wakeup_interval))
wake_up_process(consumer);

+#ifndef CONFIG_PREEMPT
/*
* If we are a non preempt kernel, the 10 second run will
* stop everything while it runs. Instead, we will call
* cond_resched and also add any time that was lost by a
* rescedule.
+ *
+ * Do a cond resched at the same frequency we would wake up
+ * the reader.
*/
- cond_resched();
+ if (cnt % wakeup_interval)
+ cond_resched();
+#endif

} while (end_tv.tv_sec < (start_tv.tv_sec + RUN_TIME) && !kill_test);
pr_info("End ring buffer hammer\n");
--
1.6.2.4

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