On 2013-01-11 10:11, majianpeng wrote:
> In func tg_may_dispatch,
>> if (throtl_slice_used(td, tg, rw))
>> throtl_start_new_slice(td, tg, rw);
> ...
>> if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
>> && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {
>
> In funcs tg_with_in_(bps/iops)_limit, it used the slice_start to count.
> So if privious slice expired, it start a new slice.This can cause hung
> task.
>
> The next steps can repeat this bug.
> 1:echo "8:48 10240" > blkio.throttle.write_bps_devic
> 2:dd if=/dev/zero of=/dev/sdd bs=1M count=1 oflag=direct
>
> Using the blktrace, the messages about throttle:
> root@kernel:/mnt/programs# blktrace -d /dev/sdd -a notify -o -|blkparse -i -
> 8,48 1 0 0.000000000 0 m N throtl / [W] new slice
> start=4294854679 end=4294854779 jiffies=4294854679
> 8,48 1 0 0.000000966 0 m N throtl / [W] extend slice
> start=4294854679 end=4294905900 jiffies=4294854679
> 8,48 1 0 0.000002553 0 m N throtl / [W] bio. bdisp=0
> sz=524288 bps=10240 iodisp=0 iops=4294967295 queued=0/0
> 8,48 1 0 0.000004788 0 m N throtl schedule work.
> delay=51200 jiffies=4294854679
> 8,48 1 0 51.304698681 0 m N throtl dispatch nr_queued=1
> read=0 write=1
> 8,48 1 0 51.304701979 0 m N throtl / [W] new slice
> start=4294905984 end=4294906084 jiffies=4294905984
> 8,48 1 0 51.304703329 0 m N throtl / [W] extend slice
> start=4294905984 end=4294957200 jiffies=4294905984
> 8,48 1 0 51.304705783 0 m N throtl schedule work.
> delay=51200 jiffies=4294905984
> 8,48 1 0 102.632697082 0 m N throtl dispatch nr_queued=1
> read=0 write=1
> 8,48 1 0 102.632700544 0 m N throtl / [W] new slice
> start=4294957312 end=4294957412 jiffies=4294957312
> 8,48 1 0 102.632701922 0 m N throtl / [W] extend slice
> start=4294957312 end=4295008600 jiffies=4294957312
> 8,48 1 0 102.632704016 0 m N throtl schedule work.
> delay=51200 jiffies=4294957312
> 8,48 1 0 153.960696503 0 m N throtl dispatch nr_queued=1
> read=0 write=1
> 8,48 1 0 153.960699797 0 m N throtl / [W] new slice
> start=4295008640 end=4295008740 jiffies=4295008640
> 8,48 1 0 153.960701153 0 m N throtl / [W] extend slice
> start=4295008640 end=4295059900 jiffies=4295008640
> 8,48 1 0 153.960703218 0 m N throtl schedule work.
> delay=51200 jiffies=4295008640
> 8,48 1 0 205.288697067 0 m N throtl dispatch nr_queued=1
> read=0 write=1
> 8,48 1 0 205.288700268 0 m N throtl / [W] new slice
> start=4295059968 end=4295060068 jiffies=4295059968
> 8,48 1 0 205.288701630 0 m N throtl / [W] extend slice
> start=4295059968 end=4295111200 jiffies=4295059968
> 8,48 1 0 205.288703784 0 m N throtl schedule work.
> delay=51200 jiffies=4295059968
> 8,48 1 0 256.616696184 0 m N throtl dispatch nr_queued=1
> read=0 write=1
> 8,48 1 0 256.616699266 0 m N throtl / [W] new slice
> start=4295111296 end=4295111396 jiffies=4295111296
> 8,48 1 0 256.616700574 0 m N throtl / [W] extend slice
> start=4295111296 end=4295162500 jiffies=4295111296
> 8,48 1 0 256.616702701 0 m N throtl schedule work.
> delay=51200 jiffies=4295111296
>
> Signed-off-by: Jianpeng Ma <[email protected]>
> ---
> block/blk-throttle.c | 15 ++++++++++-----
> 1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> index 3114622..9258789 100644
> --- a/block/blk-throttle.c
> +++ b/block/blk-throttle.c
> @@ -645,6 +645,15 @@ static bool tg_may_dispatch(struct throtl_data *td,
> struct throtl_grp *tg,
> }
>
> /*
> + * If privious slice expired,then start new slice.
> + * But counting bps and iops limit need privious slice info
> + * which ->slice_start.
> + */
> + if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
> + && tg_with_in_iops_limit(td, tg, bio, &iops_wait))
> + if (wait)
> + *wait = 0;
> + /*
> * If previous slice expired, start a new one otherwise renew/extend
> * existing slice to make sure it is at least throtl_slice interval
> * long since now.
> @@ -656,12 +665,8 @@ static bool tg_may_dispatch(struct throtl_data *td,
> struct throtl_grp *tg,
> throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
> }
>
> - if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
> - && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {
> - if (wait)
> - *wait = 0;
> + if (!(bps_wait || iops_wait))
> return 1;
> - }
>
> max_wait = max(bps_wait, iops_wait);
Looks pretty sane to me. Vivek?
--
Jens Axboe
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