Re: [PATCH 7/7] cgroups: Add a max number of tasks subsystem

Li Zefan
2011-07-26T01:25:37Z

Paul Menage wrote:
> On Mon, Jul 11, 2011 at 7:15 AM, Frederic Weisbecker <fweisbec@gmail.com> wrote:
>> /* */
>> +
>> +#ifdef CONFIG_CGROUP_MAX_TASKS
>> +SUBSYS(max_tasks)
>> +#endif
>
> I think I'd be inclined to make the naming slightly (IMO) cleaner:
> call the subsystem 'tasks' and the files 'limit' and 'count' (or maybe
> 'usage' to be more in line with memcg).
>>
>> +config CGROUP_MAX_TASKS
>> + bool "Control max number of tasks in a cgroup"
>> + depends on RESOURCE_COUNTERS
>> + help
>> + This option let the user to set up an upper bound allowed number
>> + of tasks.
>> +
>
> Needs to depend on CGROUPS too?
>

it's done implicitly, because it's inside "menuconfig CGROUPS".

>> +
>> +
>> +struct task_counter {
>> + struct res_counter res;
>> + struct cgroup_subsys_state css;
>> +};
>
> All other CSS structures put the "css" field as the first thing in the
> structure. Not sure that anything relies on that, but consistency

no as far as I know, and that's a bad thing.

> can't hurt and it probably makes the code fractionally smaller since
> the translation between CSS and task_counter becomes a no-op.
>
>> +static void task_counter_exit(struct cgroup_subsys *ss, struct cgroup *cgrp,
>> + struct cgroup *old_cgrp, struct task_struct *task)
>> +{
>> + struct task_counter *cnt = cgroup_task_counter(old_cgrp);
>> +
>> + if (cnt != &root_counter)
>> + res_counter_uncharge_until(&cnt->res, &root_counter.res, 1);
>> +}
>
> Do we even need the root_counter to be exposed in any way? Why not
> make children of the root cgroup just have a NULL parent res_counter?
>
> You'll still need a task_counter object so that the cgroups framework
> has a CSS object for cgroups housekeeping, but I don't think it needs
> to actually be used for anything.
>
> Paul
>