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Date: Wed, 17 Aug 2011 11:18:58 +0800
From: Li Zefan <lizf@cn.fujitsu.com>
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To: Frederic Weisbecker <fweisbec@gmail.com>
CC: LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Paul Menage <menage@google.com>, Johannes Weiner <hannes@cmpxchg.org>,
        Aditya Kali <adityakali@google.com>, Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH 7/8] cgroups: Add a task counter subsystem
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> diff --git a/init/Kconfig b/init/Kconfig
> index 412c21b..bea98d2d 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -690,6 +690,13 @@ config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
>  	  select this option (if, for some reason, they need to disable it
>  	  then noswapaccount does the trick).
>  
> +config CGROUP_TASK_COUNTER
> +        bool "Control number of tasks in a cgroup"

TAB

> +	depends on RESOURCE_COUNTERS
> +	help
> +	  This option let the user to set up an upper bound allowed number

will let?

> +	  of tasks inside a cgroup.
> +
>  config CGROUP_PERF
>  	bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
>  	depends on PERF_EVENTS && CGROUPS

...

> +int cgroup_task_counter_fork(struct task_struct *child)
> +{
> +	struct cgroup_subsys_state *css = child->cgroups->subsys[tasks_subsys_id];
> +	struct cgroup *cgrp = css->cgroup;
> +	struct res_counter *limit_fail_at;
> +
> +	/* Optimize for the root cgroup case, which doesn't have a limit */
> +	if (!cgrp->parent)
> +		return 0;
> +
> +	return res_counter_charge(cgroup_task_counter_res(cgrp), 1, &limit_fail_at);

I think we should change the return value of res_counter_charge.
Currently it returns -ENOMEM when we excceed limit.

> +}
> +
> +struct cgroup_subsys tasks_subsys = {
> +	.name			= "tasks",
> +	.subsys_id		= tasks_subsys_id,
> +	.create			= task_counter_create,
> +	.post_clone		= task_counter_post_clone,
> +	.destroy		= task_counter_destroy,
> +	.exit			= task_counter_exit,
> +	.can_attach_task	= task_counter_can_attach_task,
> +	.cancel_attach_task	= task_counter_cancel_attach_task,
> +	.attach_task		= task_counter_attach_task,
> +	.populate		= task_counter_populate,
> +	.early_init		= 1,

Just set early_init to 0, since this subsystem doesn't have to be
initialized early during kernel boot.

> +};