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authorOleg Nesterov <oleg@tv-sign.ru>2006-10-04 02:17:17 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-04 07:55:31 -0700
commit20e9751bd9dd6b832fd84ada27840360f7e877f1 (patch)
treec598ff9cb9e540da7f8595f2c130f3674065e018 /kernel/rcupdate.c
parent4b6c2cca6eef9cc4a15350bf1c61839e12e08b84 (diff)
[PATCH] rcu: simplify/improve batch tuning
Kill a hard-to-calculate 'rsinterval' boot parameter and per-cpu rcu_data.last_rs_qlen. Instead, it adds adds a flag rcu_ctrlblk.signaled, which records the fact that one of CPUs has sent a resched IPI since the last rcu_start_batch(). Roughly speaking, we need two rcu_start_batch()s in order to move callbacks from ->nxtlist to ->donelist. This means that when ->qlen exceeds qhimark and continues to grow, we should send a resched IPI, and then do it again after we gone through a quiescent state. On the other hand, if it was already sent, we don't need to do it again when another CPU detects overflow of the queue. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Acked-by: Paul E. McKenney <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel/rcupdate.c')
-rw-r--r--kernel/rcupdate.c11
1 files changed, 3 insertions, 8 deletions
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 523e46483b9..26bb5ffe1ef 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -71,9 +71,6 @@ static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
static int blimit = 10;
static int qhimark = 10000;
static int qlowmark = 100;
-#ifdef CONFIG_SMP
-static int rsinterval = 1000;
-#endif
static atomic_t rcu_barrier_cpu_count;
static DEFINE_MUTEX(rcu_barrier_mutex);
@@ -86,8 +83,8 @@ static void force_quiescent_state(struct rcu_data *rdp,
int cpu;
cpumask_t cpumask;
set_need_resched();
- if (unlikely(rdp->qlen - rdp->last_rs_qlen > rsinterval)) {
- rdp->last_rs_qlen = rdp->qlen;
+ if (unlikely(!rcp->signaled)) {
+ rcp->signaled = 1;
/*
* Don't send IPI to itself. With irqs disabled,
* rdp->cpu is the current cpu.
@@ -301,6 +298,7 @@ static void rcu_start_batch(struct rcu_ctrlblk *rcp)
smp_mb();
cpus_andnot(rcp->cpumask, cpu_online_map, nohz_cpu_mask);
+ rcp->signaled = 0;
}
}
@@ -628,9 +626,6 @@ void synchronize_rcu(void)
module_param(blimit, int, 0);
module_param(qhimark, int, 0);
module_param(qlowmark, int, 0);
-#ifdef CONFIG_SMP
-module_param(rsinterval, int, 0);
-#endif
EXPORT_SYMBOL_GPL(rcu_batches_completed);
EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
EXPORT_SYMBOL_GPL(call_rcu);