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SubjectRe: [PATCH v2] blk-throttle: simplify logic by token bucket algorithm
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Hi, Tejun,

I did the test for 3 levels hierarchy. It works.

Preparation
============
1) mount subsys blkio with "__DEVEL__sane_behavior"
2) Create 3 levels of directories under the blkio mount point:
mkdir 1
mkdir 1/2
mkdir 1/2/3
3) start 3 bash sessions, write their PIDs into:
1/cgroup.procs
1/2/cgroup.procs
1/2/3/cgroup.procs
4) prepare 3 10MB files on sdb(ext4 fs)

Note: in below hierarchy graph:
"[50k]" means configured value for read_bps_device is 50kB/s
"(50k)" means bandwidth reported by dd is 50kB/s

Test A: 1 process throttled by ancestor group
=============================================
Hierarchy set-up:
(echo "8:16 204800" > 1/blkio.throttle.read_bps_device)
1 [200k]
`-- 2 [-]
`-- 3 [-]

dd within group 3:
(drop cache then: dd if=10M-file-3 of=/dev/null)
Result:
206kB/s (I did same test without the token-bucket patch, The
result is 205kB/s)

dd within group 2:
(drop cache then: dd if=10M-file-2 of=/dev/null)
Result:
205kB/s


Test B: 3 processes in 3 levels of hierarchy
=============================================
Hierarchy set-up:
echo "8:16 204800" > 1/blkio.throttle.read_bps_device
echo "8:16 102400" > 1/2/blkio.throttle.read_bps_device
echo "8:16 51200" > 1/2/3/blkio.throttle.read_bps_device
1 [200k]
`-- 2 [100k]
`-- 3 [50k]
start 3 dd processes from 3 bash sessions
(dd if=10M-file-x of=/dev/null)
Result:
1 (103k)
`-- 2 (51.9k)
`-- 3 (51.4k)


best regards
Hong Zhiguo


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