From: "Paul E. McKenney" <paulmck@linux.ibm.com>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
"Paul E. McKenney" <paulmck@linux.ibm.com>
Subject: [PATCH tip/core/rcu 14/18] rcu: Update jiffies_to_sched_qs and adjust_jiffies_till_sched_qs() comments
Date: Tue, 26 Mar 2019 16:13:10 -0700 [thread overview]
Message-ID: <20190326231314.19518-14-paulmck@linux.ibm.com> (raw)
In-Reply-To: <20190326231253.GA18343@linux.ibm.com>
This commit better documents the jiffies_to_sched_qs default-value
strategy used by adjust_jiffies_till_sched_qs()
Reported-by: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
---
kernel/rcu/tree.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 466299c3d2da..e117732bcd5d 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -406,7 +406,7 @@ static bool rcu_kick_kthreads;
*/
static ulong jiffies_till_sched_qs = ULONG_MAX;
module_param(jiffies_till_sched_qs, ulong, 0444);
-static ulong jiffies_to_sched_qs; /* Adjusted version of above if not default */
+static ulong jiffies_to_sched_qs; /* See adjust_jiffies_till_sched_qs(). */
module_param(jiffies_to_sched_qs, ulong, 0444); /* Display only! */
/*
@@ -424,6 +424,7 @@ static void adjust_jiffies_till_sched_qs(void)
WRITE_ONCE(jiffies_to_sched_qs, jiffies_till_sched_qs);
return;
}
+ /* Otherwise, set to third fqs scan, but bound below on large system. */
j = READ_ONCE(jiffies_till_first_fqs) +
2 * READ_ONCE(jiffies_till_next_fqs);
if (j < HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV)
--
2.17.1
next prev parent reply other threads:[~2019-03-26 23:14 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-26 23:12 [PATCH tip/core/rcu 0/18] Miscellaneous fixes for v5.2 Paul E. McKenney
2019-03-26 23:12 ` [PATCH tip/core/rcu 01/18] rcu: Unconditionally expedite during suspend/hibernate Paul E. McKenney
2019-03-26 23:12 ` [PATCH tip/core/rcu 02/18] rcu: Avoid unnecessary softirq when system is idle Paul E. McKenney
2019-03-26 23:12 ` [PATCH tip/core/rcu 03/18] rcu: rcu_qs -- Use raise_softirq_irqoff to not save irqs twice Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 04/18] rcu: Make exit_rcu() handle non-preempted RCU readers Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 05/18] rcu: Set rcutree.kthread_prio sysfs access to read-only Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 06/18] MAINTAINERS: RCU now has its own email list Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 07/18] MAINTAINERS: Add -rcu branch name ("dev") Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 08/18] rcu: Move common code out of if-else block Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 09/18] rcu: Allow rcu_nocbs= to specify all CPUs Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 10/18] rcu: Report error for bad rcu_nocbs= parameter values Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 11/18] rcu: Fix self-wakeups for grace-period kthread Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 12/18] rcu: Default jiffies_to_sched_qs to jiffies_till_sched_qs Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 13/18] rcu: Do a single rhp->func read in rcu_head_after_call_rcu() Paul E. McKenney
2019-03-26 23:13 ` Paul E. McKenney [this message]
2019-03-26 23:13 ` [PATCH tip/core/rcu 15/18] rcu: Fix force_qs_rnp() header comment Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 16/18] rcu: Eliminate redundant NULL-pointer check Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 17/18] rcu: Fix typo in tree_exp.h comment Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 18/18] rcu: Correct READ_ONCE()/WRITE_ONCE() for ->rcu_read_unlock_special Paul E. McKenney
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