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Date: Wed, 1 Nov 2006 15:50:01 -0800
From: "Paul Menage" <menage@google.com>
To: "Matt Helsley" <matthltc@us.ibm.com>
Subject: Re: [ckrm-tech] [RFC] Resource Management - Infrastructure choices
Cc: vatsa@in.ibm.com, "Pavel Emelianov" <xemul@openvz.org>, dev@openvz.org,
       sekharan@us.ibm.com, ckrm-tech@lists.sourceforge.net, balbir@in.ibm.com,
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On 11/1/06, Matt Helsley <matthltc@us.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
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