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Commit bb4e2c08 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Eliminate unused expedited_normal counter 



Expedited grace periods no longer fall back to normal grace periods
in response to lock contention, given that expedited grace periods
now use the rcu_node tree so as to avoid contention.  This commit
therfore removes the expedited_normal counter.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent d78973c3

Documentation/RCU/trace.txt

+1 −4
Original line number Diff line number Diff line
@@ -237,7 +237,7 @@ o "ktl" is the low-order 16 bits (in hexadecimal) of the count of 


The output of "cat rcu/rcu_preempt/rcuexp" looks as follows:



s=21872 wd1=0 wd2=0 wd3=5 n=0 enq=0 sc=21872

s=21872 wd1=0 wd2=0 wd3=5 enq=0 sc=21872



These fields are as follows:
@@ -249,9 +249,6 @@ o "wd1", "wd2", and "wd3" are the number of times that an attempt 
	completed an expedited grace period that satisfies the attempted

	request.  "Our work is done."



o	"n" is number of times that a concurrent CPU-hotplug operation

	forced a fallback to a normal grace period.



o	"enq" is the number of quiescent states still outstanding.



o	"sc" is the number of times that the attempt to start a

kernel/rcu/tree.h

+0 −1
Original line number Diff line number Diff line
@@ -521,7 +521,6 @@ struct rcu_state { 
	struct mutex exp_mutex;			/* Serialize expedited GP. */

	struct mutex exp_wake_mutex;		/* Serialize wakeup. */

	unsigned long expedited_sequence;	/* Take a ticket. */

	atomic_long_t expedited_normal;		/* # fallbacks to normal. */

	atomic_t expedited_need_qs;		/* # CPUs left to check in. */

	struct swait_queue_head expedited_wq;	/* Wait for check-ins. */

	int ncpus_snap;				/* # CPUs seen last time. */

kernel/rcu/tree_trace.c

+1 −2
Original line number Diff line number Diff line
@@ -194,9 +194,8 @@ static int show_rcuexp(struct seq_file *m, void *v) 
		s2 += atomic_long_read(&rdp->exp_workdone2);

		s3 += atomic_long_read(&rdp->exp_workdone3);

	}

	seq_printf(m, "s=%lu wd0=%lu wd1=%lu wd2=%lu wd3=%lu n=%lu enq=%d sc=%lu\n",

	seq_printf(m, "s=%lu wd0=%lu wd1=%lu wd2=%lu wd3=%lu enq=%d sc=%lu\n",

		   rsp->expedited_sequence, s0, s1, s2, s3,

		   atomic_long_read(&rsp->expedited_normal),

		   atomic_read(&rsp->expedited_need_qs),

		   rsp->expedited_sequence / 2);

	return 0;