Commit 6308f347 authored Feb 14, 2018 by Paul E. McKenney

rcu: Remove SRCU throttling

The code in srcu_gp_end() inserts a delay every 0x3ff grace periods in
order to prevent SRCU grace-period work from consuming an entire CPU
when there is a long sequence of expedited SRCU grace-period requests.
However, all of SRCU's grace-period work is carried out in workqueues,
which are in turn within kthreads, which are automatically throttled as
needed by the scheduler. In particular, if there is plenty of idle time,
there is no point in throttling.

This commit therefore removes the expedited SRCU grace-period throttling.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

parent a72da917

kernel/rcu/srcutree.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -596,9 +596,7 @@ static void srcu_gp_end(struct srcu_struct *sp)
		ULONG_CMP_LT(gpseq, sp->srcu_gp_seq_needed)) {
		srcu_gp_start(sp);
		spin_unlock_irq_rcu_node(sp);
		/* Throttle expedited grace periods: Should be rare! */
		srcu_reschedule(sp, rcu_seq_ctr(gpseq) & 0x3ff
		? 0 : SRCU_INTERVAL);
		srcu_reschedule(sp, 0);
		} else {
		spin_unlock_irq_rcu_node(sp);
		}

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