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Message-ID: <76cba167-d2c4-8105-a04d-5e74eab2592f@huawei.com>
Date: Sat, 14 May 2022 17:29:59 +0800
From: "yukuai (C)" <yukuai3@...wei.com>
To: <bvanassche@....org>, <hch@...radead.org>, <axboe@...nel.dk>
CC: <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<yi.zhang@...wei.com>
Subject: Re: [PATCH -next v2] block: update nsecs[] in part_stat_show() and
diskstats_show()
friendly ping ...
在 2022/05/05 8:58, yukuai (C) 写道:
> friendly ping ...
>
> 在 2022/04/24 10:43, yukuai (C) 写道:
>> friendly ping ...
>>
>> 在 2022/04/15 16:06, Yu Kuai 写道:
>>> commit 86d7331299fd("block: update io_ticks when io hang") fixed that
>>> %util will be zero for iostat when io is hanged, however, avgqu-sz is
>>> still zero while it represents the number of io that are hunged. On the
>>> other hand, for some slow device, if an io is started before and done
>>> after diskstats is read, the avgqu-sz will be miscalculated.
>>>
>>> To fix the problem, update 'nsecs[]' when part_stat_show() or
>>> diskstats_show() is called. In order to do that, add 'stat_time' in
>>> struct block_device and 'rq_stat_time' in struct request to record the
>>> time. And during iteration, update 'nsecs[]' for each inflight request.
>>>
>>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>>> ---
>>> Changes in v2:
>>> - remove other cleanup patches.
>>>
>>> block/bdev.c | 2 ++
>>> block/blk-mq.c | 62 ++++++++++++++++++++++++++++++++++++++-
>>> block/blk-mq.h | 2 ++
>>> block/genhd.c | 62 +++++++++++++++++++++++++--------------
>>> include/linux/blk-mq.h | 2 ++
>>> include/linux/blk_types.h | 5 ++++
>>> 6 files changed, 112 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/block/bdev.c b/block/bdev.c
>>> index 7bf88e591aaf..da0471f7492d 100644
>>> --- a/block/bdev.c
>>> +++ b/block/bdev.c
>>> @@ -487,9 +487,11 @@ struct block_device *bdev_alloc(struct gendisk
>>> *disk, u8 partno)
>>> bdev = I_BDEV(inode);
>>> mutex_init(&bdev->bd_fsfreeze_mutex);
>>> spin_lock_init(&bdev->bd_size_lock);
>>> + spin_lock_init(&bdev->bd_stat_lock);
>>> bdev->bd_partno = partno;
>>> bdev->bd_inode = inode;
>>> bdev->bd_queue = disk->queue;
>>> + bdev->stat_time = 0;
>>> bdev->bd_stats = alloc_percpu(struct disk_stats);
>>> if (!bdev->bd_stats) {
>>> iput(inode);
>>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>>> index 3fe3226aad1b..ebb4db535794 100644
>>> --- a/block/blk-mq.c
>>> +++ b/block/blk-mq.c
>>> @@ -128,6 +128,48 @@ struct mq_inflight {
>>> unsigned int inflight[2];
>>> };
>>> +static bool blk_mq_check_inflight_with_stat(struct request *rq, void
>>> *priv,
>>> + bool reserved)
>>> +{
>>> + struct mq_inflight *mi = priv;
>>> +
>>> + if ((!mi->part->bd_partno || rq->part == mi->part) &&
>>> + blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT) {
>>> + u64 stat_time;
>>> +
>>> + mi->inflight[rq_data_dir(rq)]++;
>>> + if (!rq->part)
>>> + return true;
>>> +
>>> + stat_time = READ_ONCE(rq->stat_time_ns);
>>> + /*
>>> + * This might fail if 'req->stat_time_ns' is updated in
>>> + * blk_account_io_done().
>>> + */
>>> + if (likely(cmpxchg(&rq->stat_time_ns, stat_time,
>>> + rq->part->stat_time) == stat_time)) {
>>> + int sgrp = op_stat_group(req_op(rq));
>>> + u64 duation = stat_time ?
>>> + rq->part->stat_time - stat_time :
>>> + rq->part->stat_time - rq->start_time_ns;
>>> +
>>> + part_stat_add(rq->part, nsecs[sgrp], duation);
>>> + }
>>> + }
>>> +
>>> + return true;
>>> +}
>>> +
>>> +unsigned int blk_mq_in_flight_with_stat(struct request_queue *q,
>>> + struct block_device *part)
>>> +{
>>> + struct mq_inflight mi = { .part = part };
>>> +
>>> + blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight_with_stat,
>>> &mi);
>>> +
>>> + return mi.inflight[0] + mi.inflight[1];
>>> +}
>>> +
>>> static bool blk_mq_check_inflight(struct request *rq, void *priv,
>>> bool reserved)
>>> {
>>> @@ -369,6 +411,7 @@ static struct request *blk_mq_rq_ctx_init(struct
>>> blk_mq_alloc_data *data,
>>> rq->start_time_ns = ktime_get_ns();
>>> else
>>> rq->start_time_ns = 0;
>>> + rq->stat_time_ns = 0;
>>> rq->part = NULL;
>>> #ifdef CONFIG_BLK_RQ_ALLOC_TIME
>>> rq->alloc_time_ns = alloc_time_ns;
>>> @@ -870,7 +913,24 @@ static void __blk_account_io_done(struct request
>>> *req, u64 now)
>>> part_stat_lock();
>>> update_io_ticks(req->part, jiffies, true);
>>> part_stat_inc(req->part, ios[sgrp]);
>>> - part_stat_add(req->part, nsecs[sgrp], now - req->start_time_ns);
>>> +
>>> + if (queue_is_mq(req->q)) {
>>> + u64 stat_time = READ_ONCE(req->stat_time_ns);
>>> +
>>> + /*
>>> + * This might fail if 'req->stat_time_ns' is updated during
>>> + * blk_mq_check_inflight_with_stat().
>>> + */
>>> + if (likely(cmpxchg(&req->stat_time_ns, stat_time, now) ==
>>> + stat_time)) {
>>> + u64 duation = stat_time ? now - stat_time :
>>> + now - req->start_time_ns;
>>> +
>>> + part_stat_add(req->part, nsecs[sgrp], duation);
>>> + }
>>> + } else {
>>> + part_stat_add(req->part, nsecs[sgrp], now -
>>> req->start_time_ns);
>>> + }
>>> part_stat_unlock();
>>> }
>>> diff --git a/block/blk-mq.h b/block/blk-mq.h
>>> index 9bad3057c1f3..e6c2c523c8de 100644
>>> --- a/block/blk-mq.h
>>> +++ b/block/blk-mq.h
>>> @@ -193,6 +193,8 @@ unsigned int blk_mq_in_flight(struct
>>> request_queue *q,
>>> struct block_device *part);
>>> void blk_mq_in_flight_rw(struct request_queue *q, struct
>>> block_device *part,
>>> unsigned int inflight[2]);
>>> +unsigned int blk_mq_in_flight_with_stat(struct request_queue *q,
>>> + struct block_device *part);
>>> static inline void blk_mq_put_dispatch_budget(struct request_queue *q,
>>> int budget_token)
>>> diff --git a/block/genhd.c b/block/genhd.c
>>> index b8b6759d670f..36144fe8872b 100644
>>> --- a/block/genhd.c
>>> +++ b/block/genhd.c
>>> @@ -932,25 +932,52 @@ ssize_t part_size_show(struct device *dev,
>>> return sprintf(buf, "%llu\n", bdev_nr_sectors(dev_to_bdev(dev)));
>>> }
>>> -ssize_t part_stat_show(struct device *dev,
>>> - struct device_attribute *attr, char *buf)
>>> +static inline void part_set_stat_time(struct block_device *part)
>>> +{
>>> + u64 now = ktime_get_ns();
>>> +
>>> +again:
>>> + part->stat_time = now;
>>> +
>>> + if (part->bd_partno) {
>>> + part = bdev_whole(part);
>>> + goto again;
>>> + }
>>> +}
>>> +
>>> +static inline void part_get_stat_info(struct block_device *bdev,
>>> + struct disk_stats *stat,
>>> + unsigned int *inflight)
>>> {
>>> - struct block_device *bdev = dev_to_bdev(dev);
>>> struct request_queue *q = bdev_get_queue(bdev);
>>> - struct disk_stats stat;
>>> - unsigned int inflight;
>>> - if (queue_is_mq(q))
>>> - inflight = blk_mq_in_flight(q, bdev);
>>> - else
>>> - inflight = part_in_flight(bdev);
>>> + if (queue_is_mq(q)) {
>>> + part_stat_lock();
>>> + spin_lock(&bdev->bd_stat_lock);
>>> + part_set_stat_time(bdev);
>>> + *inflight = blk_mq_in_flight_with_stat(q, bdev);
>>> + spin_unlock(&bdev->bd_stat_lock);
>>> + part_stat_unlock();
>>> + } else {
>>> + *inflight = part_in_flight(bdev);
>>> + }
>>> - if (inflight) {
>>> + if (*inflight) {
>>> part_stat_lock();
>>> update_io_ticks(bdev, jiffies, true);
>>> part_stat_unlock();
>>> }
>>> - part_stat_read_all(bdev, &stat);
>>> + part_stat_read_all(bdev, stat);
>>> +}
>>> +
>>> +ssize_t part_stat_show(struct device *dev,
>>> + struct device_attribute *attr, char *buf)
>>> +{
>>> + struct block_device *bdev = dev_to_bdev(dev);
>>> + struct disk_stats stat;
>>> + unsigned int inflight;
>>> +
>>> + part_get_stat_info(bdev, &stat, &inflight);
>>> return sprintf(buf,
>>> "%8lu %8lu %8llu %8u "
>>> "%8lu %8lu %8llu %8u "
>>> @@ -1239,17 +1266,8 @@ 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;
>>> - if (queue_is_mq(gp->queue))
>>> - inflight = blk_mq_in_flight(gp->queue, hd);
>>> - else
>>> - inflight = part_in_flight(hd);
>>> -
>>> - if (inflight) {
>>> - part_stat_lock();
>>> - update_io_ticks(hd, jiffies, true);
>>> - part_stat_unlock();
>>> - }
>>> - part_stat_read_all(hd, &stat);
>>> +
>>> + part_get_stat_info(hd, &stat, &inflight);
>>> seq_printf(seqf, "%4d %7d %pg "
>>> "%lu %lu %lu %u "
>>> "%lu %lu %lu %u "
>>> diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
>>> index 7aa5c54901a9..387e475fedd4 100644
>>> --- a/include/linux/blk-mq.h
>>> +++ b/include/linux/blk-mq.h
>>> @@ -108,6 +108,8 @@ struct request {
>>> u64 start_time_ns;
>>> /* Time that I/O was submitted to the device. */
>>> u64 io_start_time_ns;
>>> + /* Time that I/O was counted in part_get_stat_info(). */
>>> + u64 stat_time_ns;
>>> #ifdef CONFIG_BLK_WBT
>>> unsigned short wbt_flags;
>>> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
>>> index 046a34c81ec4..4014b0c0ef16 100644
>>> --- a/include/linux/blk_types.h
>>> +++ b/include/linux/blk_types.h
>>> @@ -65,6 +65,11 @@ struct block_device {
>>> struct super_block *bd_fsfreeze_sb;
>>> struct partition_meta_info *bd_meta_info;
>>> +
>>> + /* Prevent part_get_stat_info() to be called concurrently */
>>> + spinlock_t bd_stat_lock;
>>> + /* Will be set when part_get_stat_info() is called */
>>> + u64 stat_time;
>>> #ifdef CONFIG_FAIL_MAKE_REQUEST
>>> bool bd_make_it_fail;
>>> #endif
>>>
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