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Message-ID: <201301111711251317275@gmail.com>
Date: Fri, 11 Jan 2013 17:11:28 +0800
From: majianpeng <majianpeng@...il.com>
To: axboe <axboe@...nel.dk>
Cc: linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH] blkcg: Before starting a new slice, firstly count bps/iops limit in func tg_may_dispatch.
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@...nel:/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 <majianpeng@...il.com>
---
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);
--
1.7.9.5
Jianpeng Ma
Thanks!
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