linux-kernel - Re: [PATCH] rcu-scale: change rcu-scale report.

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Date:   Tue, 22 Jun 2021 18:48:30 +0800
From:   "Han, Jiangong" <Jiangong.Han@...driver.com>
To:     paulmck@...nel.org
Cc:     dave@...olabs.net, josh@...htriplett.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        joel@...lfernandes.org, linux-kernel@...r.kernel.org,
        rcu@...r.kernel.org
Subject: Re: [PATCH] rcu-scale: change rcu-scale report.

Sorry, my the comment is wrong, and the correct comment should be like 
below, and I had modify this, and I had resend one more applying review 
patch email for this.

Thanks for you time.

Br,

Jiangong.

----------------------------------
     rcu-scale: rcu-scale returns one less than the real number of gps 
in the dmesg report.

     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

----------------------------------



  2021/6/10 上午4:37, Paul E. McKenney 写道:
> [Please note: This e-mail is from an EXTERNAL e-mail address]
>
> On Sat, Jun 05, 2021 at 03:00:19PM +0800, Jiangong.Han wrote:
>> The report on rcu-scale shows there are N grace periods, and gps
>> are listed from 0 to N-1.
>> This commit make writer_n_durations stores the counts of gps,
>> change the listed gps index begin from 1 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:   131 28004391
>>      [ 8316.538498] rcu-scale:    0 writer-duration:   132 27996410
>>
>> to
>>      [ 8306.087880] rcu-scale: writer 0 gps: 133
>>      ......
>>      [ 8307.864630] rcu-scale:    0 writer-duration:     1 44003961
>>      [ 8307.935711] rcu-scale:    0 writer-duration:     2 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@...driver.com>
> You lost me on this one.  Why is this helpful?  And how does the change
> shown below actually result in the output shown above, given that
> rcu_scale_cleanup() still starts j at zero?
>
>                                                          Thanx, Paul
>
>> ---
>>   kernel/rcu/rcuscale.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> 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,
>> --
>> 2.17.1
>>