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Message-ID: <d11bce89-d647-dbbf-a73f-d4b7498c04ae@huawei.com>
Date: Fri, 8 Apr 2022 14:52:10 +0800
From: "yukuai (C)" <yukuai3@...wei.com>
To: <axboe@...nel.dk>, <mpatocka@...hat.com>, <snitzer@...hat.com>
CC: <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<yi.zhang@...wei.com>
Subject: Re: [PATCH -next 3/3] block: update nsecs[] in part_get_stat()
在 2022/04/01 11:42, yukuai (C) 写道:
> 在 2022/03/17 19:26, 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.
> Friendly ping... Does anyone have any suggestions on this apporch ?
friendlig ping ...
>
> Thanks,
> Kuai
>>
>> Fixes: 5b18b5a73760 ("block: delete part_round_stats and switch to
>> less precise counting")
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>> ---
>> block/bdev.c | 2 ++
>> block/blk-mq.c | 63 ++++++++++++++++++++++++++++++++++++++-
>> block/blk-mq.h | 2 ++
>> block/genhd.c | 25 ++++++++++++++--
>> include/linux/blk-mq.h | 2 ++
>> include/linux/blk_types.h | 5 ++++
>> 6 files changed, 95 insertions(+), 4 deletions(-)
>>
>> diff --git a/block/bdev.c b/block/bdev.c
>> index 13de871fa816..5dced478f190 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 c33fb378b168..7a14d4058b14 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -149,6 +149,48 @@ unsigned int blk_mq_in_flight(struct
>> request_queue *q,
>> return mi.inflight[0] + mi.inflight[1];
>> }
>> +static bool blk_mq_check_inflight_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' happen to be 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_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_stat, &mi);
>> +
>> + return mi.inflight[0] + mi.inflight[1];
>> +}
>> +
>> void blk_mq_in_flight_rw(struct request_queue *q, struct
>> block_device *part,
>> unsigned int inflight[2])
>> {
>> @@ -368,6 +410,7 @@ 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;
>> @@ -874,7 +917,25 @@ 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' happen to be updated
>> + * in part_get_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->part->stat_time);
>> + }
>> part_stat_unlock();
>> }
>> diff --git a/block/blk-mq.h b/block/blk-mq.h
>> index 7d1acf8e1e51..37941f5f1d08 100644
>> --- a/block/blk-mq.h
>> +++ b/block/blk-mq.h
>> @@ -189,6 +189,8 @@ static inline bool blk_mq_hw_queue_mapped(struct
>> blk_mq_hw_ctx *hctx)
>> unsigned int blk_mq_in_flight(struct request_queue *q,
>> struct block_device *part);
>> +unsigned int blk_mq_in_flight_stat(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]);
>> diff --git a/block/genhd.c b/block/genhd.c
>> index f2c7de2e7ca9..31603c7aff49 100644
>> --- a/block/genhd.c
>> +++ b/block/genhd.c
>> @@ -953,6 +953,19 @@ ssize_t part_size_show(struct device *dev,
>> return sprintf(buf, "%llu\n", bdev_nr_sectors(dev_to_bdev(dev)));
>> }
>> +static 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 unsigned int part_get_stat(struct block_device *bdev,
>> struct disk_stats *stat)
>> @@ -960,10 +973,16 @@ static unsigned int part_get_stat(struct
>> block_device *bdev,
>> struct request_queue *q = bdev_get_queue(bdev);
>> unsigned int inflight;
>> - if (queue_is_mq(q))
>> - inflight = blk_mq_in_flight(q, bdev);
>> - else
>> + if (queue_is_mq(q)) {
>> + spin_lock(&bdev->bd_stat_lock);
>> + part_stat_lock();
>> + part_set_stat_time(bdev);
>> + inflight = blk_mq_in_flight_stat(q, bdev);
>> + part_stat_unlock();
>> + spin_unlock(&bdev->bd_stat_lock);
>> + } else {
>> inflight = part_in_flight(bdev);
>> + }
>> if (inflight) {
>> part_stat_lock();
>> diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
>> index e512da636e0f..e98f07d1741c 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 accounted in part_get_stat() */
>> + 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 c6ed4a559e6a..5cd399b5670d 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() to be called concurrently */
>> + spinlock_t bd_stat_lock;
>> + /* Will be set when part_stat_show() or diskstats_show() is
>> called */
>> + u64 stat_time;
>> #ifdef CONFIG_FAIL_MAKE_REQUEST
>> bool bd_make_it_fail;
>> #endif
>>
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