From: Ildar Ismagilov <devix84@gmail.com>
To: unlisted-recipients:; (no To-header on input)
Cc: devix84@gmail.com,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Josh Triplett <josh@joshtriplett.org>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH 2/2] srcu: reduce scans of srcu_data in counter wrap check
Date: Wed, 31 Jan 2018 22:42:21 +0300 [thread overview]
Message-ID: <20180131194221.28544-1-devix84@gmail.com> (raw)
This patch reduce scans of srcu_data in case of a srcu_struct
tree have more than one levels
Signed-off-by: Ildar Ismagilov <devix84@gmail.com>
---
kernel/rcu/srcutree.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index c54617280245..2268381706d2 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -500,6 +500,7 @@ static void srcu_gp_end(struct srcu_struct *sp)
{
unsigned long cbdelay;
bool cbs;
+ bool last_lvl;
int cpu;
unsigned long flags;
unsigned long gpseq;
@@ -532,7 +533,8 @@ static void srcu_gp_end(struct srcu_struct *sp)
rcu_for_each_node_breadth_first(sp, snp) {
raw_spin_lock_irq_rcu_node(snp);
cbs = false;
- if (snp >= sp->level[rcu_num_lvls - 1])
+ last_lvl = snp >= sp->level[rcu_num_lvls - 1];
+ if (last_lvl)
cbs = snp->srcu_have_cbs[idx] == gpseq;
snp->srcu_have_cbs[idx] = gpseq;
rcu_seq_set_state(&snp->srcu_have_cbs[idx], 1);
@@ -545,7 +547,7 @@ static void srcu_gp_end(struct srcu_struct *sp)
srcu_schedule_cbs_snp(sp, snp, mask, cbdelay);
/* Occasionally prevent srcu_data counter wrap. */
- if (!(gpseq & counter_wrap_check))
+ if (!(gpseq & counter_wrap_check) && last_lvl)
for (cpu = snp->grplo; cpu <= snp->grphi; cpu++) {
sdp = per_cpu_ptr(sp->sda, cpu);
raw_spin_lock_irqsave_rcu_node(sdp, flags);
--
2.11.0
next reply other threads:[~2018-01-31 19:42 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-31 19:42 Ildar Ismagilov [this message]
2018-02-03 9:18 ` [PATCH 2/2] srcu: reduce scans of srcu_data in counter wrap check Paul E. McKenney
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