From: Frederic Weisbecker <frederic@kernel.org>
To: "Paul E . McKenney" <paulmck@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
rcu <rcu@vger.kernel.org>, Uladzislau Rezki <urezki@gmail.com>,
Neeraj Upadhyay <quic_neeraju@quicinc.com>,
Joel Fernandes <joel@joelfernandes.org>,
Giovanni Gherdovich <ggherdovich@suse.cz>
Subject: [PATCH 5/9] rcu: Add rcutree.lazy_enabled boot parameter
Date: Wed, 31 May 2023 12:17:32 +0200 [thread overview]
Message-ID: <20230531101736.12981-6-frederic@kernel.org> (raw)
In-Reply-To: <20230531101736.12981-1-frederic@kernel.org>
Allow to overwrite the arbitrary default number of lazy callbacks
threshold that is currently set to 100. This allows for tuning between
powersaving, throughtput and memory consumption expectations. As a
bonus, setting this value to 0 disables lazy callbacks.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
Documentation/admin-guide/kernel-parameters.txt | 5 +++++
kernel/rcu/tree.c | 3 ++-
2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 505978cfb548..dd2be4249061 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4798,6 +4798,11 @@
Set threshold of queued RCU callbacks beyond which
batch limiting is disabled.
+ rcutree.qhimark_lazy = [KNL]
+ Set threshold of queued lazy RCU callbacks beyond which
+ batch must be flushed to the main queue. If set to 0,
+ disable lazy queue.
+
rcutree.qlowmark= [KNL]
Set threshold of queued RCU callbacks below which
batch limiting is re-enabled.
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9b98d87fa22e..e33c0d889216 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -390,6 +390,7 @@ static long qovld_calc = -1; // No pre-initialization lock acquisitions!
module_param(blimit, long, 0444);
module_param(qhimark, long, 0444);
+module_param(qhimark_lazy, long, 0444);
module_param(qlowmark, long, 0444);
module_param(qovld, long, 0444);
@@ -2655,7 +2656,7 @@ __call_rcu_common(struct rcu_head *head, rcu_callback_t func, bool lazy_in)
kasan_record_aux_stack_noalloc(head);
local_irq_save(flags);
rdp = this_cpu_ptr(&rcu_data);
- lazy = lazy_in && !rcu_async_should_hurry();
+ lazy = lazy_in && qhimark_lazy && !rcu_async_should_hurry();
/* Add the callback to our list. */
if (unlikely(!rcu_segcblist_is_enabled(&rdp->cblist))) {
--
2.40.1
next prev parent reply other threads:[~2023-05-31 10:18 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-31 10:17 [PATCH 0/9] rcu: Support for lazy callbacks on !CONFIG_RCU_NOCB_CPU Frederic Weisbecker
2023-05-31 10:17 ` [PATCH 1/9] rcu: Assume IRQS disabled from rcu_report_dead() Frederic Weisbecker
2023-06-02 22:51 ` Joel Fernandes
2023-05-31 10:17 ` [PATCH 2/9] rcu: Use rcu_segcblist_segempty() instead of open coding it Frederic Weisbecker
2023-06-02 23:00 ` Joel Fernandes
2023-07-05 12:21 ` Frederic Weisbecker
2023-06-13 8:44 ` Zhuo, Qiuxu
2023-05-31 10:17 ` [PATCH 3/9] rcu: Rename jiffies_till_flush to jiffies_lazy_flush Frederic Weisbecker
2023-06-01 17:15 ` kernel test robot
2023-06-01 17:15 ` kernel test robot
2023-06-01 22:40 ` kernel test robot
2023-05-31 10:17 ` [PATCH 4/9] rcu: Introduce lazy queue's own qhimark Frederic Weisbecker
2023-06-03 1:23 ` Joel Fernandes
2023-07-05 12:45 ` Frederic Weisbecker
2023-05-31 10:17 ` Frederic Weisbecker [this message]
2023-06-13 6:57 ` [PATCH 5/9] rcu: Add rcutree.lazy_enabled boot parameter Zhuo, Qiuxu
2023-07-05 12:42 ` Frederic Weisbecker
2023-05-31 10:17 ` [PATCH 6/9] rcu/nocb: Rename was_alldone to was_pending Frederic Weisbecker
2023-05-31 10:17 ` [PATCH 7/9] rcu: Implement lazyness on the main segcblist level Frederic Weisbecker
2023-05-31 10:17 ` [PATCH 8/9] rcu: Make segcblist flags test strict Frederic Weisbecker
2023-05-31 10:17 ` [PATCH 9/9] rcu: Support lazy callbacks with CONFIG_RCU_NOCB_CPU=n Frederic Weisbecker
2023-07-05 12:41 ` [PATCH 0/9] rcu: Support for lazy callbacks on !CONFIG_RCU_NOCB_CPU Frederic Weisbecker
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