On Tue, Jun 22, 2021 at 06:37:08PM +0800, Jiangong.Han wrote:
> The dmesg report on rcu-scale shows there are N grace periods, and gps
> are listed from 0 to N.
> This commit make writer_n_durations stores the counts of gps,
> and shows there are N+1 gps, change the listed gps index begin from 0 to N.
>
> From
> [ 8306.087880] rcu-scale: writer 0 gps: 133
> ......
> [ 8307.864630] rcu-scale: 0 writer-duration: 0 44003961
> [ 8307.935711] rcu-scale: 0 writer-duration: 1 32003582
> ......
> [ 8316.472860] rcu-scale: 0 writer-duration: 132 28004391
> [ 8316.538498] rcu-scale: 0 writer-duration: 133 27996410
>
> to
> [ 8306.087880] rcu-scale: writer 0 gps: 134
> ......
> [ 8307.864630] rcu-scale: 0 writer-duration: 0 44003961
> [ 8307.935711] rcu-scale: 0 writer-duration: 1 32003582
> ......
> [ 8316.472860] rcu-scale: 0 writer-duration: 132 28004391
> [ 8316.538498] rcu-scale: 0 writer-duration: 133 27996410
>
> Signed-off-by: Jiangong.Han <jiangong.han@xxxxxxxxxxxxx>
Much better, thank you!
As usual, I could not resist the urge to wordsmith a bit, so could
you please check the version below to make sure that I didn't mess
something up?
Thanx, Paul
------------------------------------------------------------------------
commit 4c154a9103443b22aef8667ab64278d12372e64f
Author: Jiangong.Han <jiangong.han@xxxxxxxxxxxxx>
Date: Tue Jun 22 18:37:08 2021 +0800
rcuscale: Console output claims too few grace periods
The rcuscale console output claims N grace periods, numbered from zero
to N, which means that there were really N+1 grace periods. The root
cause of this bug is that rcu_scale_writer() stores the number of the
last grace period (numbered from zero) into writer_n_durations[me]
instead of the number of grace periods. This commit therefore assigns
the actual number of grace periods to writer_n_durations[me], and also
makes the corresponding adjustment to the loop outputting per-grace-period
measurements.
Sample of old console output:
rcu-scale: writer 0 gps: 133
......
rcu-scale: 0 writer-duration: 0 44003961
rcu-scale: 0 writer-duration: 1 32003582
......
rcu-scale: 0 writer-duration: 132 28004391
rcu-scale: 0 writer-duration: 133 27996410
Sample of new console output:
rcu-scale: writer 0 gps: 134
......
rcu-scale: 0 writer-duration: 0 44003961
rcu-scale: 0 writer-duration: 1 32003582
......
rcu-scale: 0 writer-duration: 132 28004391
rcu-scale: 0 writer-duration: 133 27996410
Signed-off-by: Jiangong.Han <jiangong.han@xxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index dca51fe9c73f..2cc34a22a506 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -487,7 +487,7 @@ rcu_scale_writer(void *arg)
if (gp_async) {
cur_ops->gp_barrier();
}
- writer_n_durations[me] = i_max;
+ writer_n_durations[me] = i_max + 1;
torture_kthread_stopping("rcu_scale_writer");
return 0;
}
@@ -561,7 +561,7 @@ rcu_scale_cleanup(void)
wdpp = writer_durations[i];
if (!wdpp)
continue;
- for (j = 0; j <= writer_n_durations[i]; j++) {
+ for (j = 0; j < writer_n_durations[i]; j++) {
wdp = &wdpp[j];
pr_alert("%s%s %4d writer-duration: %5d %llu\n",
scale_type, SCALE_FLAG,
