Re: [RFC] patch

[Alexander Nikiforov <a.nikiforov-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>]

Hi Kirill, thanks for your reply

On 04/02/2012 02:29 PM, Kirill A. Shutemov wrote:
> On Mon, Apr 02, 2012 at 08:22:14AM +0400, Alexander Nikiforov wrote:
>
> I think it should be part of task counter css, not core.
> CC list updated.
Maybe, I need time to think about your suggestion.
>> @@ -4558,6 +4594,22 @@ void cgroup_fork(struct task_struct *child)
>>   	child->cgroups = current->cgroups;
>>   	get_css_set(child->cgroups);
>>   	INIT_LIST_HEAD(&child->cg_list);
>> +
>> +	struct cgroupfs_root *root;
>> +
>> +	/* send event to the userspace */
>> +	mutex_lock(&cgroup_mutex);
>> +	for_each_active_root(root) {
>> +		struct cgroup *cgrp;
>> +		struct fe_eventfd_list *ev;
>> +
>> +		cgrp = task_cgroup_from_root(child, root);
>> +
>> +		list_for_each_entry(ev,&cgrp->fe_notify, list) {
>> +			eventfd_signal(ev->eventfd, 1);
>> +		}
>> +	}
>> +	mutex_unlock(&cgroup_mutex);
>>   }
> How does it affect performance?
One cycle with active roots, one inside task_cgroup_from_root() through 
cg_links and through events. I don't think what this is significant, 
maybe I wrong.
>
>>
>>   /**
>> @@ -4653,6 +4705,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
>>   {
>>   	struct css_set *cg;
>>   	int i;
>> +	struct cgroupfs_root *root;
>>
>>   	/*
>>   	 * Unlink from the css_set task list if necessary.
>> @@ -4666,6 +4719,20 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
>>   		write_unlock(&css_set_lock);
>>   	}
>>
>> +	/* send event to the userspace */
>> +	mutex_lock(&cgroup_mutex);
>> +	for_each_active_root(root) {
>> +		struct cgroup *cgrp;
>> +		struct fe_eventfd_list *ev;
>> +
>> +		cgrp = task_cgroup_from_root(tsk, root);
>> +
>> +		list_for_each_entry(ev,&cgrp->fe_notify, list) {
>> +			eventfd_signal(ev->eventfd, 1);
>> +		}
>> +	}
>> +	mutex_unlock(&cgroup_mutex);
>> +
> I think it's racy. You need to notify userspace after reassigning the
> task, not before.
You are right.
>>   	/* Reassign the task to the init_css_set. */
>>   	task_lock(tsk);
>>   	cg = tsk->cgroups;
>


-- 
Best regards,
      Alex Nikiforov,
      Mobile SW, Advanced Software Group,
      Moscow R&D center, Samsung Electronics