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authorSteven Rostedt <srostedt@redhat.com>2009-05-06 18:36:59 -0400
committerSteven Rostedt <rostedt@goodmis.org>2009-05-06 18:36:59 -0400
commit3e07a4f680adc66dfa175aa5021aedf340251b12 (patch)
treec245b416cf3d88e4c2f1d0ff43d0021e59b20b47
parent6634ff26cce2da04e5c2a5481bcb8888e7d01786 (diff)
ring-buffer: change test to be more latency friendly
The ring buffer benchmark/test runs a producer for 10 seconds. This is done with preemption and interrupts enabled. But if the kernel is not compiled with CONFIG_PREEMPT, it basically stops everything but interrupts for 10 seconds. Although this is just a test and is not for production, this attribute can be quite annoying. It can also spawn badness elsewhere. This patch solves the issues by calling "cond_resched" when the system is not compiled with CONFIG_PREEMPT. It also keeps track of the time spent to call cond_resched such that it does not go against the time calculations. That is, if the task schedules away, the time scheduled out is removed from the test data. Note, this only works for non PREEMPT because we do not know when the task is scheduled out if we have PREEMPT enabled. [ Impact: prevent test from stopping the world for 10 seconds ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
-rw-r--r--kernel/trace/ring_buffer_benchmark.c31
1 files changed, 31 insertions, 0 deletions
diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index dcd75e9e49f..a26fc67b63b 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -185,6 +185,35 @@ static void ring_buffer_consumer(void)
complete(&read_done);
}
+/*
+ * 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.
+ */
+#ifdef CONFIG_PREEMPT
+static void sched_if_needed(struct timeval *start_tv, struct timeval *end_tv)
+{
+}
+#else
+static void sched_if_needed(struct timeval *start_tv, struct timeval *end_tv)
+{
+ struct timeval tv;
+
+ cond_resched();
+ do_gettimeofday(&tv);
+ if (tv.tv_usec < end_tv->tv_usec) {
+ tv.tv_usec += 1000000;
+ tv.tv_sec--;
+ }
+ start_tv->tv_sec += tv.tv_sec - end_tv->tv_sec;
+ start_tv->tv_usec += tv.tv_usec - end_tv->tv_usec;
+ if (start_tv->tv_usec > 1000000) {
+ start_tv->tv_usec -= 1000000;
+ start_tv->tv_sec++;
+ }
+}
+#endif
+
static void ring_buffer_producer(void)
{
struct timeval start_tv;
@@ -221,6 +250,8 @@ static void ring_buffer_producer(void)
if (consumer && !(++cnt % wakeup_interval))
wake_up_process(consumer);
+ sched_if_needed(&start_tv, &end_tv);
+
} while (end_tv.tv_sec < (start_tv.tv_sec + RUN_TIME) && !kill_test);
pr_info("End ring buffer hammer\n");