linux-kernel - Re: [ckrm-tech] [RFC] Resource Management

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Date:	Thu, 02 Nov 2006 11:03:30 +0530
From:	Balbir Singh <balbir@...ibm.com>
To:	Matt Helsley <matthltc@...ibm.com>
CC:	Paul Menage <menage@...gle.com>, vatsa@...ibm.com,
	Pavel Emelianov <xemul@...nvz.org>, dev@...nvz.org,
	sekharan@...ibm.com, ckrm-tech@...ts.sourceforge.net,
	haveblue@...ibm.com, linux-kernel@...r.kernel.org, pj@....com,
	dipankar@...ibm.com, rohitseth@...gle.com
Subject: Re: [ckrm-tech] [RFC] Resource Management - Infrastructure choices

Matt Helsley wrote:
> On Wed, 2006-11-01 at 15:50 -0800, Paul Menage wrote:
>> On 11/1/06, Matt Helsley <matthltc@...ibm.com> wrote:
>>> On Wed, 2006-11-01 at 23:42 +0530, Srivatsa Vaddagiri wrote:
>>>> On Wed, Nov 01, 2006 at 12:30:13PM +0300, Pavel Emelianov wrote:
>>> <snip>
>>>
>>>>>>   - Support movement of all threads of a process from one group
>>>>>>     to another atomically?
>>>>> I propose such a solution: if a user asks to move /proc/<pid>
>>>>> then move the whole task with threads.
>>>>> If user asks to move /proc/<pid>/task/<tid> then move just
>>>>> a single thread.
>>>>>
>>>>> What do you think?
>>>> Isnt /proc/<pid> listed also in /proc/<pid>/task/<tid>?
>>>>
>>>> For ex:
>>>>
>>>>       # ls /proc/2906/task
>>>>       2906  2907  2908  2909
>>>>
>>>> 2906 is the main thread which created the remaining threads.
>>>>
>>>> This would lead to an ambiguity when user does something like below:
>>>>
>>>>       echo 2906 > /some_res_file_system/some_new_group
>>>>
>>>> Is he intending to move just the main thread, 2906, to the new group or
>>>> all the threads? It could be either.
>>>>
>>>> This needs some more thought ...
>>>         I thought the idea was to take in a proc path instead of a single
>>> number. You could then distinguish between the whole thread group and
>>> individual threads by parsing the string. You'd move a single thread if
>>> you find both the tgid and the tid. If you only get a tgid you'd move
>>> the whole thread group. So:
>>>
>>> <pid>                   -> if it's a thread group leader move the whole
>>>                            thread group, otherwise just move the thread
>>> /proc/<tgid>            -> move the whole thread group
>>> /proc/<tgid>/task/<tid> -> move the thread
>>>
>>>
>>>         Alternatives that come to mind are:
>>>
>>> 1. Read a flag with the pid
>>> 2. Use a special file which expects only thread groups as input
>> I think that having a "tasks" file and a "threads" file in each
>> container directory would be a clean way to handle it:
>>
>> "tasks" : read/write complete process members
>> "threads" : read/write individual thread members
>>
>> Paul
> 
> Seems like a good idea to me -- that certainly avoids complex parsing.
> 
> Cheers,
> 	-Matt Helsley
> 

Yeah, sounds like a good idea. We need to give the controllers some control
over whether they support task movement, thread movement or both.

-- 

	Balbir Singh,
	Linux Technology Center,
	IBM Software Labs
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