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Message-ID: <4234595e-f34a-5ea1-b91b-9831215f556e@huaweicloud.com>
Date: Fri, 15 Dec 2023 17:29:17 +0800
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Subject: Re: [PATCH v2 2/2] md: don't account sync_io if iostats of the disk
 is disabled
To: Song Liu <song@kernel.org>, linan666@huaweicloud.com
Cc: axboe@kernel.dk, linux-raid@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
 yukuai3@huawei.com, yi.zhang@huawei.com, houtao1@huawei.com,
 yangerkun@huawei.com
References: <20231215013931.3329455-1-linan666@huaweicloud.com>
 <20231215013931.3329455-3-linan666@huaweicloud.com>
 <CAPhsuW7aQoh-sHqJ1de+z7rHZLbbXVimUtxae1pBbzOQxXAB_Q@mail.gmail.com>
From: Li Nan <linan666@huaweicloud.com>
In-Reply-To: <CAPhsuW7aQoh-sHqJ1de+z7rHZLbbXVimUtxae1pBbzOQxXAB_Q@mail.gmail.com>
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在 2023/12/15 17:08, Song Liu 写道:
> On Thu, Dec 14, 2023 at 5:41 PM <linan666@huaweicloud.com> wrote:
>>
>> From: Li Nan <linan122@huawei.com>
>>
>> If iostats is disabled, disk_stats will not be updated and
>> part_stat_read_accum() only returns a constant value. In this case,
>> continuing to count sync_io and to check is_mddev_idle() is no longer
>> meaningful.
>>
>> Signed-off-by: Li Nan <linan122@huawei.com>
>> ---
>>   drivers/md/md.h | 3 ++-
>>   drivers/md/md.c | 4 ++++
>>   2 files changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/md/md.h b/drivers/md/md.h
>> index 1a4f976951c1..75f5c5d04e71 100644
>> --- a/drivers/md/md.h
>> +++ b/drivers/md/md.h
>> @@ -589,7 +589,8 @@ static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sect
>>
>>   static inline void md_sync_acct_bio(struct bio *bio, unsigned long nr_sectors)
>>   {
>> -       md_sync_acct(bio->bi_bdev, nr_sectors);
>> +       if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
>> +               md_sync_acct(bio->bi_bdev, nr_sectors);
> 
> Do we need the same check for md_sync_acct()?
> 
>>   }
>>
>>   struct md_personality
>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>> index 1d71b2a9af03..18bbceb0ffd6 100644
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -8502,6 +8502,10 @@ static int is_mddev_idle(struct mddev *mddev, int init)
>>          rcu_read_lock();
>>          rdev_for_each_rcu(rdev, mddev) {
>>                  struct gendisk *disk = rdev->bdev->bd_disk;
>> +
>> +               if (blk_queue_io_stat(mddev->queue))
>> +                       continue;
> 
> This looks weird. Do you mean
> 
>     if (!blk_queue_io_stat(disk->queue))
> 
> Note that I changed two things here: 1) add "!"; 2) check disk, not mddev.
> 
> Did I miss something?
> 
> Thanks,
> Song
> 

Yeah... It's my bad. I will fix it in v3.

>> +
>>                  curr_events =
>>                          (long long)part_stat_read_accum(disk->part0, sectors) -
>>                                atomic64_read(&disk->sync_io);
>> --
>> 2.39.2
>>
> 
> .

-- 
Thanks,
Nan