From cd618d102b753a3f6823b297ac5c5d03d4e7f0c2 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 8 Jan 2019 13:41:26 -0800 Subject: [PATCH] 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: Paul E. McKenney --- kernel/rcu/rcutorture.c | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index f6e85faa4ff4..0955f3a20952 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -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); -- 2.11.0