diff mbox series

[1/6] rcu-tasks: Use accurate runstart time for RCU Tasks boot-time testing

Message ID 20230105004501.1771332-1-paulmck@kernel.org (mailing list archive)
State New, archived
Headers show
Series [1/6] rcu-tasks: Use accurate runstart time for RCU Tasks boot-time testing | expand

Commit Message

Paul E. McKenney Jan. 5, 2023, 12:44 a.m. UTC 
From: Zqiang <qiang1.zhang@intel.com>

Currently, test_rcu_tasks_callback() reads from the jiffies counter only
once when this function is invoked.  This introduces inaccuracies because
of the latencies induced by the synchronize_rcu_tasks*() invocations.
This commit therefore re-reads the jiffies counter at the beginning
of each test, thus avoiding penalizing later tests for the latencies
induced by earlier tests.

Therefore, this commit at the start of each RCU Tasks test, re-fetch the
jiffies time as the runstart time.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/tasks.h | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index fe9840d90e960..c418aa1c038a9 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1815,23 +1815,21 @@  static void test_rcu_tasks_callback(struct rcu_head *rhp)
 
 static void rcu_tasks_initiate_self_tests(void)
 {
-	unsigned long j = jiffies;
-
 	pr_info("Running RCU-tasks wait API self tests\n");
 #ifdef CONFIG_TASKS_RCU
-	tests[0].runstart = j;
+	tests[0].runstart = jiffies;
 	synchronize_rcu_tasks();
 	call_rcu_tasks(&tests[0].rh, test_rcu_tasks_callback);
 #endif
 
 #ifdef CONFIG_TASKS_RUDE_RCU
-	tests[1].runstart = j;
+	tests[1].runstart = jiffies;
 	synchronize_rcu_tasks_rude();
 	call_rcu_tasks_rude(&tests[1].rh, test_rcu_tasks_callback);
 #endif
 
 #ifdef CONFIG_TASKS_TRACE_RCU
-	tests[2].runstart = j;
+	tests[2].runstart = jiffies;
 	synchronize_rcu_tasks_trace();
 	call_rcu_tasks_trace(&tests[2].rh, test_rcu_tasks_callback);
 #endif