linux-kernel - Re: Per container statistics (containerstats)

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Message-ID: <4668C271.80404@linux.vnet.ibm.com>
Date:	Fri, 08 Jun 2007 08:14:01 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	menage@...gle.com, dev@...ru, xemul@...ru, serue@...ibm.com,
	vatsa@...ibm.com, ebiederm@...ssion.com, haveblue@...ibm.com,
	svaidy@...ux.vnet.ibm.com, balbir@...ibm.com, pj@....com,
	cpw@....com, ckrm-tech@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, containers@...ts.osdl.org,
	mbligh@...gle.com, rohitseth@...gle.com, devel@...nvz.org
Subject: Re: Per container statistics (containerstats)

Andrew Morton wrote:
> On Fri, 08 Jun 2007 07:51:12 +0530 Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> 
>> Andrew Morton wrote:
>>> I'd have hoped to see containerstats.c in here.
>>>
>> The current statistics code is really small, so it fit into taskstats.c.
>> May be in the future, we could re-factor it and move it out.
> 
> I was referring to your userspace tool which reads this stuff.  The one
> which you described in the changelog.
> 

Ahh.. yes.. I'll make the changes and repost with the tool.

>>>> +	rcu_read_lock();
>>>> +
>>>> +	for_each_root(root) {
>>>> +		if (!root->subsys_bits)
>>>> +			continue;
>>>> +		root_cont = &root->top_container;
>>>> +		get_first_subsys(root_cont, NULL, &subsys_id);
>>>> +		do_each_thread(g, p) {
>>> this needs tasklist_lock?
>>>
>> rcu_read_lock() should be fine. From Eric's patch at
>>
>> 2.6.17-mm2 - proc-remove-tasklist_lock-from-proc_pid_readdir.patch
>>
>> The patch mentions that "We don't need the tasklist_lock to safely
>> iterate through processes anymore."
>>
> 
> oh, OK.  rcu_read_lock() is the new lock_kernel() - always hard to tell
> what it's locking.
> 

:-) I'll add a comment to make it clearer.


-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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