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Subject[PATCH tip/core/rcu 06/10] rcu: Run grace-period kthreads at real-time priority
Date
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

This is a experimental commit that attempts to better handle high-load
situations.

Not-yet-signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
init/Kconfig | 1 -
kernel/rcu/tree.c | 10 +++++++++-
kernel/rcu/tree_plugin.h | 4 ----
3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 9afb971497f4..8787131d0f5c 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -669,7 +669,6 @@ config RCU_BOOST
config RCU_KTHREAD_PRIO
int "Real-time priority to use for RCU worker threads"
range 1 99
- depends on RCU_BOOST
default 1
help
This option specifies the SCHED_FIFO priority value that will be
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 5987fdc85fc4..7a8d7e0d23f6 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -156,6 +156,10 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
static void invoke_rcu_core(void);
static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);

+/* rcuc/rcub kthread realtime priority */
+static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO;
+module_param(kthread_prio, int, 0644);
+
/*
* Track the rcutorture test sequence number and the update version
* number within a given test. The rcutorture_testseq is incremented
@@ -3599,15 +3603,19 @@ static int __init rcu_spawn_gp_kthread(void)
unsigned long flags;
struct rcu_node *rnp;
struct rcu_state *rsp;
+ struct sched_param sp;
struct task_struct *t;

rcu_scheduler_fully_active = 1;
for_each_rcu_flavor(rsp) {
- t = kthread_run(rcu_gp_kthread, rsp, "%s", rsp->name);
+ t = kthread_create(rcu_gp_kthread, rsp, "%s", rsp->name);
BUG_ON(IS_ERR(t));
rnp = rcu_get_root(rsp);
raw_spin_lock_irqsave(&rnp->lock, flags);
rsp->gp_kthread = t;
+ sp.sched_priority = kthread_prio;
+ sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
+ wake_up_process(t);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
rcu_spawn_nocb_kthreads();
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 81ff8b9a5a39..dcb32638f88b 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -34,10 +34,6 @@

#include "../locking/rtmutex_common.h"

-/* rcuc/rcub kthread realtime priority */
-static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO;
-module_param(kthread_prio, int, 0644);
-
/*
* Control variables for per-CPU and per-rcu_node kthreads. These
* handle all flavors of RCU.
--
1.8.1.5


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