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SubjectRe: [PATCH v2] blk-throttle: simplify logic by token bucket algorithm
On Tue, Oct 15 2013, Hong zhi guo wrote:
> 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)

Thanks for doing this testing, and the work to move to a token based
system. It makes a lot of sense. I've been investigating a token based
scheduler for blk-mq as well, since that could feasibly be made to scale
as well.

--
Jens Axboe



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