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Message-ID: <a4d8f6b5-cc8e-204e-1039-5f2b98042bdd@huaweicloud.com>
Date: Tue, 7 Mar 2023 18:44:49 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Yu Kuai <yukuai1@...weicloud.com>, axboe@...nel.dk, agk@...hat.com,
snitzer@...nel.org, dm-devel@...hat.com, kbusch@...nel.org,
hch@....de, sagi@...mberg.me, guz.fnst@...fujitsu.com
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-nvme@...ts.infradead.org, yi.zhang@...wei.com,
yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH -next RFC] block: count 'ios' and 'sectors' when io is
done for bio-based device
Hi,
在 2023/02/28 9:01, Yu Kuai 写道:
> Hi,
>
> friendly ping ...
>
> Thanks,
> Kuai
>
> 在 2023/02/23 17:12, Yu Kuai 写道:
>> From: Yu Kuai <yukuai3@...wei.com>
>>
>> While using iostat for raid, I observed very strange 'await'
>> occasionally, and turns out it's due to that 'ios' and 'sectors' is
>> counted in bdev_start_io_acct(), while 'nsecs' is counted in
>> bdev_end_io_acct(). I'm not sure why they are ccounted like that
>> but I think this behaviour is obviously wrong because user will get
>> wrong disk stats.
>>
>> Fix the problem by counting 'ios' and 'sectors' when io is done, like
>> what rq-based device does.
Can anyone help to review this change? Or is there any reason to count
'ios' and 'sectors' when io is started?
Thanks,
Kuai
>>
>> Fixes: 394ffa503bc4 ("blk: introduce generic io stat accounting help
>> function")
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>> ---
>> block/blk-core.c | 16 ++++++----------
>> drivers/md/dm.c | 6 +++---
>> drivers/nvme/host/multipath.c | 8 ++++----
>> include/linux/blkdev.h | 5 ++---
>> 4 files changed, 15 insertions(+), 20 deletions(-)
>>
>> diff --git a/block/blk-core.c b/block/blk-core.c
>> index 82b5b2c53f1e..fe1d320f5f07 100644
>> --- a/block/blk-core.c
>> +++ b/block/blk-core.c
>> @@ -953,16 +953,11 @@ void update_io_ticks(struct block_device *part,
>> unsigned long now, bool end)
>> }
>> }
>> -unsigned long bdev_start_io_acct(struct block_device *bdev,
>> - unsigned int sectors, enum req_op op,
>> +unsigned long bdev_start_io_acct(struct block_device *bdev, enum
>> req_op op,
>> unsigned long start_time)
>> {
>> - const int sgrp = op_stat_group(op);
>> -
>> part_stat_lock();
>> update_io_ticks(bdev, start_time, false);
>> - part_stat_inc(bdev, ios[sgrp]);
>> - part_stat_add(bdev, sectors[sgrp], sectors);
>> part_stat_local_inc(bdev, in_flight[op_is_write(op)]);
>> part_stat_unlock();
>> @@ -978,13 +973,12 @@ EXPORT_SYMBOL(bdev_start_io_acct);
>> */
>> unsigned long bio_start_io_acct(struct bio *bio)
>> {
>> - return bdev_start_io_acct(bio->bi_bdev, bio_sectors(bio),
>> - bio_op(bio), jiffies);
>> + return bdev_start_io_acct(bio->bi_bdev, bio_op(bio), jiffies);
>> }
>> EXPORT_SYMBOL_GPL(bio_start_io_acct);
>> void bdev_end_io_acct(struct block_device *bdev, enum req_op op,
>> - unsigned long start_time)
>> + unsigned int sectors, unsigned long start_time)
>> {
>> const int sgrp = op_stat_group(op);
>> unsigned long now = READ_ONCE(jiffies);
>> @@ -992,6 +986,8 @@ void bdev_end_io_acct(struct block_device *bdev,
>> enum req_op op,
>> part_stat_lock();
>> update_io_ticks(bdev, now, true);
>> + part_stat_inc(bdev, ios[sgrp]);
>> + part_stat_add(bdev, sectors[sgrp], sectors);
>> part_stat_add(bdev, nsecs[sgrp], jiffies_to_nsecs(duration));
>> part_stat_local_dec(bdev, in_flight[op_is_write(op)]);
>> part_stat_unlock();
>> @@ -1001,7 +997,7 @@ EXPORT_SYMBOL(bdev_end_io_acct);
>> void bio_end_io_acct_remapped(struct bio *bio, unsigned long
>> start_time,
>> struct block_device *orig_bdev)
>> {
>> - bdev_end_io_acct(orig_bdev, bio_op(bio), start_time);
>> + bdev_end_io_acct(orig_bdev, bio_op(bio), bio_sectors(bio),
>> start_time);
>> }
>> EXPORT_SYMBOL_GPL(bio_end_io_acct_remapped);
>> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
>> index eace45a18d45..f5cc330bb549 100644
>> --- a/drivers/md/dm.c
>> +++ b/drivers/md/dm.c
>> @@ -512,10 +512,10 @@ static void dm_io_acct(struct dm_io *io, bool end)
>> sectors = io->sectors;
>> if (!end)
>> - bdev_start_io_acct(bio->bi_bdev, sectors, bio_op(bio),
>> - start_time);
>> + bdev_start_io_acct(bio->bi_bdev, bio_op(bio), start_time);
>> else
>> - bdev_end_io_acct(bio->bi_bdev, bio_op(bio), start_time);
>> + bdev_end_io_acct(bio->bi_bdev, bio_op(bio), sectors,
>> + start_time);
>> if (static_branch_unlikely(&stats_enabled) &&
>> unlikely(dm_stats_used(&md->stats))) {
>> diff --git a/drivers/nvme/host/multipath.c
>> b/drivers/nvme/host/multipath.c
>> index fc39d01e7b63..9171452e2f6d 100644
>> --- a/drivers/nvme/host/multipath.c
>> +++ b/drivers/nvme/host/multipath.c
>> @@ -123,9 +123,8 @@ void nvme_mpath_start_request(struct request *rq)
>> return;
>> nvme_req(rq)->flags |= NVME_MPATH_IO_STATS;
>> - nvme_req(rq)->start_time = bdev_start_io_acct(disk->part0,
>> - blk_rq_bytes(rq) >> SECTOR_SHIFT,
>> - req_op(rq), jiffies);
>> + nvme_req(rq)->start_time = bdev_start_io_acct(disk->part0,
>> req_op(rq),
>> + jiffies);
>> }
>> EXPORT_SYMBOL_GPL(nvme_mpath_start_request);
>> @@ -136,7 +135,8 @@ void nvme_mpath_end_request(struct request *rq)
>> if (!(nvme_req(rq)->flags & NVME_MPATH_IO_STATS))
>> return;
>> bdev_end_io_acct(ns->head->disk->part0, req_op(rq),
>> - nvme_req(rq)->start_time);
>> + blk_rq_bytes(rq) >> SECTOR_SHIFT,
>> + nvme_req(rq)->start_time);
>> }
>> void nvme_kick_requeue_lists(struct nvme_ctrl *ctrl)
>> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
>> index d1aee08f8c18..941304f17492 100644
>> --- a/include/linux/blkdev.h
>> +++ b/include/linux/blkdev.h
>> @@ -1446,11 +1446,10 @@ static inline void blk_wake_io_task(struct
>> task_struct *waiter)
>> wake_up_process(waiter);
>> }
>> -unsigned long bdev_start_io_acct(struct block_device *bdev,
>> - unsigned int sectors, enum req_op op,
>> +unsigned long bdev_start_io_acct(struct block_device *bdev, enum
>> req_op op,
>> unsigned long start_time);
>> void bdev_end_io_acct(struct block_device *bdev, enum req_op op,
>> - unsigned long start_time);
>> + unsigned int sectors, unsigned long start_time);
>> unsigned long bio_start_io_acct(struct bio *bio);
>> void bio_end_io_acct_remapped(struct bio *bio, unsigned long
>> start_time,
>>
>
> .
>
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