Message-ID: <20240823120510.61853-1-ioworker0@gmail.com>
Date: Fri, 23 Aug 2024 20:05:02 +0800
From: Lance Yang <ioworker0@...il.com>
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Subject: Re: [BUG] cgroupv2/blk: inconsistent I/O behavior in Cgroup v2 with set device wbps and wiops

My bad, I got tied up with some stuff :(

Hmm... tried your debug patch today, but my test results are different from
yours. So let's take a look at direct IO with raw disk first.

```
$ lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda      8:0    0   90G  0 disk
├─sda1   8:1    0    1G  0 part /boot/efi
└─sda2   8:2    0 88.9G  0 part /
sdb      8:16   0   10G  0 disk

$ cat  /sys/block/sda/queue/scheduler
none [mq-deadline]

$ cat  /sys/block/sda/queue/rotational
0

$ cat  /sys/block/sdb/queue/rotational
0

$ cat  /sys/block/sdb/queue/scheduler
none [mq-deadline]

$ cat /boot/config-6.11.0-rc3+ |grep CONFIG_CGROUP_
# CONFIG_CGROUP_FAVOR_DYNMODS is not set
CONFIG_CGROUP_WRITEBACK=y
CONFIG_CGROUP_SCHED=y
CONFIG_CGROUP_PIDS=y
CONFIG_CGROUP_RDMA=y
CONFIG_CGROUP_FREEZER=y
CONFIG_CGROUP_HUGETLB=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CGROUP_CPUACCT=y
CONFIG_CGROUP_PERF=y
CONFIG_CGROUP_BPF=y
CONFIG_CGROUP_MISC=y
# CONFIG_CGROUP_DEBUG is not set
CONFIG_CGROUP_NET_PRIO=y
CONFIG_CGROUP_NET_CLASSID=y

$ cd /sys/fs/cgroup/test/ && cat cgroup.controllers
cpu io memory pids

$ cat io.weight
default 100

$ cat io.prio.class
no-change
```

With wiops, the result is as follows:

```
$ echo "8:16 wbps=10485760 wiops=100000" > io.max

$ dd if=/dev/zero of=/dev/sdb bs=50M count=1 oflag=direct
1+0 records in
1+0 records out
52428800 bytes (52 MB, 50 MiB) copied, 5.05893 s, 10.4 MB/s

$ dmesg -T
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 2984 ffff0000fb3a8f00
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 6176 ffff0000fb3a97c0
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 7224 ffff0000fb3a9180
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 16384 ffff0000fb3a8640
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 16384 ffff0000fb3a9400
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 16384 ffff0000fb3a8c80
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 16384 ffff0000fb3a9040
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 16384 ffff0000fb3a92c0
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 4096 ffff0000fb3a8000
[Fri Aug 23 11:04:08 2024] blk_throtl_dispatch_work_fn: bio done 2984 ffff0000fb3a8f00
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 1400 ffff0000fb3a8f00
[Fri Aug 23 11:04:08 2024] blk_throtl_dispatch_work_fn: bio done 6176 ffff0000fb3a97c0
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 3616 ffff0000fb3a97c0
[Fri Aug 23 11:04:08 2024] blk_throtl_dispatch_work_fn: bio done 7224 ffff0000fb3a9180
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 4664 ffff0000fb3a9180
[Fri Aug 23 11:04:09 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000fb3a8640
[Fri Aug 23 11:04:09 2024] __blk_throtl_bio: bio start 13824 ffff0000fb3a8640
[Fri Aug 23 11:04:10 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000fb3a9400
[Fri Aug 23 11:04:10 2024] __blk_throtl_bio: bio start 13824 ffff0000fb3a9400
[Fri Aug 23 11:04:11 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000fb3a8c80
[Fri Aug 23 11:04:11 2024] __blk_throtl_bio: bio start 13824 ffff0000fb3a8c80
[Fri Aug 23 11:04:12 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000fb3a9040
[Fri Aug 23 11:04:12 2024] __blk_throtl_bio: bio start 13824 ffff0000fb3a9040
[Fri Aug 23 11:04:12 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000fb3a92c0
[Fri Aug 23 11:04:12 2024] __blk_throtl_bio: bio start 13824 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 4096 ffff0000fb3a8000
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1536 ffff0000fb3a8000
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1536 ffff0000fb3a8000
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 1400 ffff0000fb3a8f00
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 3616 ffff0000fb3a97c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1056 ffff0000fb3a97c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1056 ffff0000fb3a97c0
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 4664 ffff0000fb3a9180
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 2104 ffff0000fb3a9180
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 2104 ffff0000fb3a9180
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 13824 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 11264 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 11264 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 8704 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 8704 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 6144 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 6144 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 3584 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 3584 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1024 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1024 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 13824 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 11264 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 11264 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 8704 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 8704 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 6144 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 6144 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 3584 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 3584 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1024 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1024 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 13824 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 11264 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 11264 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 8704 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 8704 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 6144 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 6144 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 3584 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 3584 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1024 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1024 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 13824 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 11264 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 11264 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 8704 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 8704 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 6144 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 6144 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 3584 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 3584 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1024 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1024 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 13824 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 11264 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 11264 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 8704 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 8704 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 6144 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 6144 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 3584 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 3584 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1024 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1024 ffff0000fb3a92c0
```

And without wiops, the result is quite different:

```
$ echo "8:16 wbps=10485760 wiops=max" > io.max

$ dd if=/dev/zero of=/dev/sdb bs=50M count=1 oflag=direct
1+0 records in
1+0 records out
52428800 bytes (52 MB, 50 MiB) copied, 5.08187 s, 10.3 MB/s

$ dmesg -T
[Fri Aug 23 10:59:10 2024] __blk_throtl_bio: bio start 2880 ffff0000c74659c0
[Fri Aug 23 10:59:10 2024] __blk_throtl_bio: bio start 6992 ffff00014f621b80
[Fri Aug 23 10:59:10 2024] __blk_throtl_bio: bio start 92528 ffff00014f620dc0
[Fri Aug 23 10:59:10 2024] blk_throtl_dispatch_work_fn: bio done 2880 ffff0000c74659c0
[Fri Aug 23 10:59:11 2024] blk_throtl_dispatch_work_fn: bio done 6992 ffff00014f621b80
[Fri Aug 23 10:59:15 2024] blk_throtl_dispatch_work_fn: bio done 92528 ffff00014f620dc0
```

Then, I retested for ext4 as you did.

```
$ lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda      8:0    0   90G  0 disk
├─sda1   8:1    0    1G  0 part /boot/efi
└─sda2   8:2    0 88.9G  0 part /
sdb      8:16   0   10G  0 disk

$ df -T /data
Filesystem     Type 1K-blocks     Used Available Use% Mounted on
/dev/sda2      ext4  91222760 54648704  31894224  64% /
```

With wiops, the result is as follows:

```
$ echo "8:0 wbps=10485760 wiops=100000" > io.max

$ rm -rf /data/file1 && dd if=/dev/zero of=/data/file1 bs=50M count=1 oflag=direct
1+0 records in
1+0 records out
52428800 bytes (52 MB, 50 MiB) copied, 5.06227 s, 10.4 MB/s

$ dmesg -T
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 2984 ffff0000fb3a8f00
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 6176 ffff0000fb3a97c0
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 7224 ffff0000fb3a9180
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 16384 ffff0000fb3a8640
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 16384 ffff0000fb3a9400
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 16384 ffff0000fb3a8c80
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 16384 ffff0000fb3a9040
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 16384 ffff0000fb3a92c0
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 4096 ffff0000fb3a8000
[Fri Aug 23 11:04:08 2024] blk_throtl_dispatch_work_fn: bio done 2984 ffff0000fb3a8f00
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 1400 ffff0000fb3a8f00
[Fri Aug 23 11:04:08 2024] blk_throtl_dispatch_work_fn: bio done 6176 ffff0000fb3a97c0
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 3616 ffff0000fb3a97c0
[Fri Aug 23 11:04:08 2024] blk_throtl_dispatch_work_fn: bio done 7224 ffff0000fb3a9180
[Fri Aug 23 11:04:08 2024] __blk_throtl_bio: bio start 4664 ffff0000fb3a9180
[Fri Aug 23 11:04:09 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000fb3a8640
[Fri Aug 23 11:04:09 2024] __blk_throtl_bio: bio start 13824 ffff0000fb3a8640
[Fri Aug 23 11:04:10 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000fb3a9400
[Fri Aug 23 11:04:10 2024] __blk_throtl_bio: bio start 13824 ffff0000fb3a9400
[Fri Aug 23 11:04:11 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000fb3a8c80
[Fri Aug 23 11:04:11 2024] __blk_throtl_bio: bio start 13824 ffff0000fb3a8c80
[Fri Aug 23 11:04:12 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000fb3a9040
[Fri Aug 23 11:04:12 2024] __blk_throtl_bio: bio start 13824 ffff0000fb3a9040
[Fri Aug 23 11:04:12 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000fb3a92c0
[Fri Aug 23 11:04:12 2024] __blk_throtl_bio: bio start 13824 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 4096 ffff0000fb3a8000
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1536 ffff0000fb3a8000
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1536 ffff0000fb3a8000
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 1400 ffff0000fb3a8f00
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 3616 ffff0000fb3a97c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1056 ffff0000fb3a97c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1056 ffff0000fb3a97c0
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 4664 ffff0000fb3a9180
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 2104 ffff0000fb3a9180
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 2104 ffff0000fb3a9180
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 13824 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 11264 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 11264 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 8704 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 8704 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 6144 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 6144 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 3584 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 3584 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1024 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1024 ffff0000fb3a8640
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 13824 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 11264 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 11264 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 8704 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 8704 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 6144 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 6144 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 3584 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 3584 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1024 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1024 ffff0000fb3a9400
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 13824 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 11264 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 11264 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 8704 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 8704 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 6144 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 6144 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 3584 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 3584 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1024 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1024 ffff0000fb3a8c80
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 13824 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 11264 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 11264 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 8704 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 8704 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 6144 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 6144 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 3584 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 3584 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1024 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1024 ffff0000fb3a9040
[Fri Aug 23 11:04:13 2024] blk_throtl_dispatch_work_fn: bio done 13824 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 11264 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 11264 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 8704 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 8704 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 6144 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 6144 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 3584 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 3584 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio start 1024 ffff0000fb3a92c0
[Fri Aug 23 11:04:13 2024] __blk_throtl_bio: bio done 1024 ffff0000fb3a92c0
```

And without wiops, the result is also quite different:

```
$ echo "8:0 wbps=10485760 wiops=max" > io.max

$ rm -rf /data/file1 && dd if=/dev/zero of=/data/file1 bs=50M count=1 oflag=direct
1+0 records in
1+0 records out
52428800 bytes (52 MB, 50 MiB) copied, 5.03759 s, 10.4 MB/s

$ dmesg -T
[Fri Aug 23 11:05:07 2024] __blk_throtl_bio: bio start 2904 ffff0000c4e9f2c0
[Fri Aug 23 11:05:07 2024] __blk_throtl_bio: bio start 5984 ffff0000c4e9e000
[Fri Aug 23 11:05:07 2024] __blk_throtl_bio: bio start 7496 ffff0000c4e9e3c0
[Fri Aug 23 11:05:07 2024] __blk_throtl_bio: bio start 16384 ffff0000c4e9eb40
[Fri Aug 23 11:05:07 2024] __blk_throtl_bio: bio start 16384 ffff0000c4e9f540
[Fri Aug 23 11:05:07 2024] __blk_throtl_bio: bio start 16384 ffff0000c4e9e780
[Fri Aug 23 11:05:07 2024] __blk_throtl_bio: bio start 16384 ffff0000c4e9ea00
[Fri Aug 23 11:05:07 2024] __blk_throtl_bio: bio start 16384 ffff0000c4e9f900
[Fri Aug 23 11:05:07 2024] __blk_throtl_bio: bio start 4096 ffff0000c4e9e8c0
[Fri Aug 23 11:05:07 2024] blk_throtl_dispatch_work_fn: bio done 2904 ffff0000c4e9f2c0
[Fri Aug 23 11:05:07 2024] blk_throtl_dispatch_work_fn: bio done 5984 ffff0000c4e9e000
[Fri Aug 23 11:05:08 2024] blk_throtl_dispatch_work_fn: bio done 7496 ffff0000c4e9e3c0
[Fri Aug 23 11:05:09 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000c4e9eb40
[Fri Aug 23 11:05:09 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000c4e9f540
[Fri Aug 23 11:05:10 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000c4e9e780
[Fri Aug 23 11:05:11 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000c4e9ea00
[Fri Aug 23 11:05:12 2024] blk_throtl_dispatch_work_fn: bio done 16384 ffff0000c4e9f900
[Fri Aug 23 11:05:12 2024] blk_throtl_dispatch_work_fn: bio done 4096 ffff0000c4e9e8c0
```

Hmm... I still hava two questions here:
1. Is wbps an average value?
2. What's the difference between setting 'max' and setting a very high value for 'wiops'?

Thanks a lot again for your time!
Lance

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