Re: [RFC PATCH v1 0/4] cgroup quota

[Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>]

On 03/09/2012 03:20 PM, Jeff Liu wrote:
> Hello,
>
> Disk quota feature has been asked at LXC list from time to time.
> Given that the project quota has already implemented in XFS for a long time, and it was also in progress for EXT4.
> So the major idea is to assign one or more project IDs(or tree ID?) to container, but leaving quota setup via cgroup
> config files, so all the tasks running at container could have project quota constraints applied.
>
> I'd like to post an initial patch sets here, the stupid implements is very simple and even crash me
> in some cases, sorry! But I would like to submit it to get more feedback to make sure I am going down
> the right road. :)
>
> Let me introduce it now.
>
> 1. Setup project quota on XFS(enabled pquota) firstly.
> For example, the "project100" is configured on "/xfs/quota_test" directory.
>
> $ cat /etc/projects
> 100:/xfs/quota_test
>
> $ cat /etc/projid
> project100:100
>
> $ sudo xfs_quota -x -c 'report -p'
> Project quota on /xfs (/dev/sda7)
>                                 Blocks
> Project ID       Used       Soft       Hard    Warn/Grace
> ---------- --------------------------------------------------
> project100          0          0          0     00 [--------]
>
> 2. Mount cgroup on /cgroup.
> cgroup on /cgroup type cgroup (rw)
>
> After that, there will have a couple of quota.XXXX files presented at /cgroup.
> $ ls -l /cgroup/quota.*
> --w------- 1 root root 0 Mar  9 18:27 /cgroup/quota.activate
> --w------- 1 root root 0 Mar  9 18:27 /cgroup/quota.add_project
> -r--r--r-- 1 root root 0 Mar  9 18:27 /cgroup/quota.all
> --w------- 1 root root 0 Mar  9 18:27 /cgroup/quota.block_limit_in_bytes
> --w------- 1 root root 0 Mar  9 18:27 /cgroup/quota.deactivate
> --w------- 1 root root 0 Mar  9 18:27 /cgroup/quota.inode_limit
> -r--r--r-- 1 root root 0 Mar  9 18:27 /cgroup/quota.projects
> --w------- 1 root root 0 Mar  9 18:27 /cgroup/quota.remove_project
> --w------- 1 root root 0 Mar  9 18:27 /cgroup/quota.reset_block_limit_in_bytes
> --w------- 1 root root 0 Mar  9 18:27 /cgroup/quota.reset_inode_limit
>
> 3. To assign a project ID to container, just echo it to quota.add_project as:
> echo "project100:100">  /cgroup/quota.add_project
>
> To get a short list of the current projects assigned to container, user can check quota.projects,
> # cat /cgroup/quota.projects
> Project ID (project100:100)	status: off
>
> The totally quota info can be check against quota.all, it will show something like below:
> # cat /cgroup/quota.all
> Project ID (project100:100)	status: off
>    block_soft_limit	9223372036854775807
>    block_hard_limit	9223372036854775807
>    block_max_usage	0
>    block_usage	0
>    inode_soft_limit	9223372036854775807
>    inode_hard_limit	9223372036854775807
>    inode_max_usage	0
>    inode_usage	0
>
> Note that about "status: off", by default, a new assigned project will in OFF state, user could
> turn it on by echo the project ID to quota.activate as below:
> # echo 100>  /cgroup/quota.activate
> # cat /cgroup/quota.all
> Project ID (project100:100)	status: on	 *now  status changed.*
>    block_soft_limit	9223372036854775807
>    block_hard_limit	9223372036854775807
>    block_max_usage	0
>    block_usage	0
>    inode_soft_limit	9223372036854775807
>    inode_hard_limit	9223372036854775807
>    inode_max_usage	0
>    inode_usage	0
>
> But it will do nothing since without quota setup.
>
> 4. To configure quota via cgroup, user need to interact with quota.inode_limit and quota.block_limit_in_bytes.
> For now, I only add a simple inode quota check to XFS, it looks something like below:
>
> # echo "100 2:4">>  /cgroup/quota.inode_limit
> # cat /cgroup/quota.all
> Project ID (project100:100)	status: on
>    block_soft_limit	9223372036854775807
>    block_hard_limit	9223372036854775807
>    block_max_usage	0
>    block_usage	0
>    inode_soft_limit	2
>    inode_hard_limit	4
>    inode_max_usage	0
>    inode_usage	0
>
> # for ((i=0; i<  6; i++)); do touch xfs/quota_test/test.$i; done
>
> Project ID (project100:100)	status: on
>    block_soft_limit	9223372036854775807
>    block_hard_limit	9223372036854775807
>    block_max_usage	0
>    block_usage	0
>    inode_soft_limit	2
>    inode_hard_limit	4
>    inode_max_usage	4
>    inode_usage	4
>
> Sorry again, above steps crashed me sometimes for now, it works just for demo purpose. :)
>
> Any criticism and suggestions are welcome!

I have mixed feelings about this. The feature is obviously welcome, but 
I am not sure if
the approach you took is the best one... I'll go through the patches 
now, and hopefully will
have a better opinion by the end =)