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Message-ID: <6e7fe188-a258-8d10-2f86-027c6b6f434c@huawei.com>
Date:   Tue, 8 Feb 2022 10:12:56 +0800
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Subject: Re: [PATCH -next] block: update io_ticks when io hang
From:   "zhangwensheng (E)" <zhangwensheng5@huawei.com>
To:     <axboe@kernel.dk>
References: <20220125091938.1799001-1-zhangwensheng5@huawei.com>
 <45c2ae11-c44e-f27d-f029-66efe96b0804@huawei.com>
CC:     <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>
In-Reply-To: <45c2ae11-c44e-f27d-f029-66efe96b0804@huawei.com>
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friendly ping...

在 2022/1/28 14:22, zhangwensheng (E) 写道:
> friendly ping...
>
> 在 2022/1/25 17:19, Zhang Wensheng 写道:
>> When the inflight IOs are slow and no new IOs are issued, we expect
>> iostat could manifest the IO hang problem. However after
>> commit 5b18b5a73760 ("block: delete part_round_stats and switch to less
>> precise counting"), io_tick and time_in_queue will not be updated until
>> the end of IO, and the avgqu-sz and %util columns of iostat will be 
>> zero.
>>
>> Because it has using stat.nsecs accumulation to express time_in_queue
>> which is not suitable to change, and may %util will express the status
>> better when io hang occur. To fix io_ticks, we use update_io_ticks and
>> inflight to update io_ticks when diskstats_show and part_stat_show
>> been called.
>>
>> Fixes: 5b18b5a73760 ("block: delete part_round_stats and switch to 
>> less precise counting")
>> Signed-off-by: Zhang Wensheng <zhangwensheng5@huawei.com>
>> ---
>>   block/genhd.c | 8 ++++++--
>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/block/genhd.c b/block/genhd.c
>> index 626c8406f21a..df0656ffb4ad 100644
>> --- a/block/genhd.c
>> +++ b/block/genhd.c
>> @@ -913,12 +913,14 @@ ssize_t part_stat_show(struct device *dev,
>>       struct disk_stats stat;
>>       unsigned int inflight;
>>   -    part_stat_read_all(bdev, &stat);
>>       if (queue_is_mq(q))
>>           inflight = blk_mq_in_flight(q, bdev);
>>       else
>>           inflight = part_in_flight(bdev);
>>   +    if (inflight)
>> +        update_io_ticks(bdev, jiffies, true);
>> +    part_stat_read_all(bdev, &stat);
>>       return sprintf(buf,
>>           "%8lu %8lu %8llu %8u "
>>           "%8lu %8lu %8llu %8u "
>> @@ -1174,12 +1176,14 @@ static int diskstats_show(struct seq_file 
>> *seqf, void *v)
>>       xa_for_each(&gp->part_tbl, idx, hd) {
>>           if (bdev_is_partition(hd) && !bdev_nr_sectors(hd))
>>               continue;
>> -        part_stat_read_all(hd, &stat);
>>           if (queue_is_mq(gp->queue))
>>               inflight = blk_mq_in_flight(gp->queue, hd);
>>           else
>>               inflight = part_in_flight(hd);
>>   +        if (inflight)
>> +            update_io_ticks(hd, jiffies, true);
>> +        part_stat_read_all(hd, &stat);
>>           seq_printf(seqf, "%4d %7d %pg "
>>                  "%lu %lu %lu %u "
>>                  "%lu %lu %lu %u "