Commit cd618d10 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcutorture: Record grace periods in forward-progress histogram 



This commit records grace periods in rcutorture's n_launders_hist[]
histogram, thus allowing rcu_torture_fwd_cb_hist() to print out the
elapsed number of grace periods between buckets.  This information
helps to determine whether a lack of forward progress is due to stalled
grace periods on the one hand or due to sluggish callback invocation on
the other.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.ibm.com>
parent 7a968bb2

kernel/rcu/rcutorture.c

+22 −7
Original line number Diff line number Diff line
@@ -1630,21 +1630,34 @@ static bool rcu_fwd_emergency_stop; 
#define MIN_FWD_CB_LAUNDERS	3	/* This many CB invocations to count. */

#define MIN_FWD_CBS_LAUNDERED	100	/* Number of counted CBs. */

#define FWD_CBS_HIST_DIV	10	/* Histogram buckets/second. */

static long n_launders_hist[2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV)];

struct rcu_launder_hist {

	long n_launders;

	unsigned long launder_gp_seq;

};

#define N_LAUNDERS_HIST (2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV))

static struct rcu_launder_hist n_launders_hist[N_LAUNDERS_HIST];

static unsigned long rcu_launder_gp_seq_start;



static void rcu_torture_fwd_cb_hist(void)

{

	unsigned long gps;

	unsigned long gps_old;

	int i;

	int j;



	for (i = ARRAY_SIZE(n_launders_hist) - 1; i > 0; i--)

		if (n_launders_hist[i] > 0)

		if (n_launders_hist[i].n_launders > 0)

			break;

	pr_alert("%s: Callback-invocation histogram (duration %lu jiffies):",

		 __func__, jiffies - rcu_fwd_startat);

	for (j = 0; j <= i; j++)

		pr_cont(" %ds/%d: %ld",

			j + 1, FWD_CBS_HIST_DIV, n_launders_hist[j]);

	gps_old = rcu_launder_gp_seq_start;

	for (j = 0; j <= i; j++) {

		gps = n_launders_hist[j].launder_gp_seq;

		pr_cont(" %ds/%d: %ld:%ld",

			j + 1, FWD_CBS_HIST_DIV, n_launders_hist[j].n_launders,

			rcutorture_seq_diff(gps, gps_old));

		gps_old = gps;

	}

	pr_cont("\n");

}
@@ -1666,7 +1679,8 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp) 
	i = ((jiffies - rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV));

	if (i >= ARRAY_SIZE(n_launders_hist))

		i = ARRAY_SIZE(n_launders_hist) - 1;

	n_launders_hist[i]++;

	n_launders_hist[i].n_launders++;

	n_launders_hist[i].launder_gp_seq = cur_ops->get_gp_seq();

	spin_unlock_irqrestore(&rcu_fwd_lock, flags);

}
@@ -1786,9 +1800,10 @@ static void rcu_torture_fwd_prog_cr(void) 
	n_max_cbs = 0;

	n_max_gps = 0;

	for (i = 0; i < ARRAY_SIZE(n_launders_hist); i++)

		n_launders_hist[i] = 0;

		n_launders_hist[i].n_launders = 0;

	cver = READ_ONCE(rcu_torture_current_version);

	gps = cur_ops->get_gp_seq();

	rcu_launder_gp_seq_start = gps;

	while (time_before(jiffies, stopat) &&

	       !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {

		rfcp = READ_ONCE(rcu_fwd_cb_head);

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