Hi,
在 2024/04/19 20:07, zhoutaiyu 写道:
Give a concrete example, a bio is throtted because of reaching bps
limit. It is then dispatched to request layer after a delay. In the
request layer, it is split and the split bio flagged with
BIO_BPS_THROTTLED will re-enter blkthrottle.
The bio with BIO_BPS_THROTTLED should not be throttled for its bytes
again. However, when the bps_limit and iops_limit are both set and
sq->queue is not empty, the bio will be throttled again even the tg is
still within iops limit.
I don't understand here, split bio should be throttled by iops limit
again, this is expected. If you mean that that throtl time calculated
by iops_limit is wrong, you need to provide more informatiom.
Test scrips:
cgpath=/sys/fs/cgroup/blkio/test0
mkdir -p $cgpath
echo "8:0 10485760" > $cgpath/blkio.throttle.write_bps_device
echo "8:16 100000" > $cgpath/blkio.throttle.write_iops_device
What? 8:0 and 8:16?
for ((i=0;i<50;i++));do
fio -rw=write -direct=1 -bs=4M -iodepth=8 -size=200M -numjobs=1 \
-time_based=1 -runtime=30 -name=testt_$i -filename=testf_$i > /dev/null &
echo $! > $cgpath/tasks
done
The output of iostat:
Device: ... wMB/s ...
sdb ... 3.75 ...
sdb ... 2.50 ...
sdb ... 3.75 ...
sdb ... 2.50 ...
sdb ... 3.75 ...
In order to fix this problem, early throttled the bio only when
sq->queue is no empty and the bio is not flagged with BIO_BPS_THROTTLED.
Signed-off-by: zhoutaiyu <zhoutaiyu@xxxxxxxxxxxx>
---
block/blk-throttle.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index f4850a6..499c006 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -913,7 +913,8 @@ static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
* queued.
*/
BUG_ON(tg->service_queue.nr_queued[rw] &&
- bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
+ bio != throtl_peek_queued(&tg->service_queue.queued[rw]) &&
+ !bio_flagged(bio, BIO_BPS_THROTTLED));
/* If tg->bps = -1, then BW is unlimited */
if ((bps_limit == U64_MAX && iops_limit == UINT_MAX) ||
@@ -2201,7 +2202,7 @@ bool __blk_throtl_bio(struct bio *bio)
throtl_downgrade_check(tg);
throtl_upgrade_check(tg);
/* throtl is FIFO - if bios are already queued, should queue */
- if (sq->nr_queued[rw])
+ if (sq->nr_queued[rw] && !bio_flagged(bio, BIO_BPS_THROTTLED))
No, this change is wrong. Split IO will not be throttled by iops limit
anymore.
Thanks,
Kuai
break;
/* if above limits, break to queue */
