Re: cgroups(7): documenting cgroups v2 thread mode

[Tejun Heo]

Hello,

On Tue, Jan 02, 2018 at 07:24:01PM +0100, Michael Kerrisk (man-pages) wrote:
>        2. We write the string "threaded" to each of the domain invalid
>           cgroups  under  y,  in  order  to  convert  them to the type
>           threaded.  As a consequence of this step, all threads  under
>           the  threaded  root  now  have  the  type  threaded  and the
>           threaded subtree is now fully usable.   The  requirement  to
>           write  "threaded"  to each of these cgroups is somewhat cumâ
>           bersome, but allows for possible future  extensions  to  the
>           thread-mode model.
> 
>           âââââââââââââââââââââââââââââââââââââââââââââââââââââââ
>           âFIXME                                                â
>           âââââââââââââââââââââââââââââââââââââââââââââââââââââââ
>           âRe  the preceding paragraphs... Are there other reaâ â
>           âsosn  for  the  (cumbersome)  requirement  to  write â
>           â'threaded'  to  each of the cgroup.type files in the â
>           âthreaded subtrees? Tejun Heo mentioned  the  followâ â
>           âing:                                                 â
>           â                                                     â
>           â    Consistency w/ the cgroups right under the root  â
>           â    cgroup.  Because they can be both domains and    â
>           â    threadroots, we can't switch the children over   â
>           â    to thread mode automatically.  Doing that for    â
>           â    cgroups further down in the hierarchy would be   â
>           â    really inconsistent.                             â
>           â                                                     â
>           âBut,  it's  not  clear  to  me  how  "Doing that for â
>           âcgroups further  down  in  the  hierarchy  would  be â
>           âreally inconsistent", since in the current implemenâ â
>           âtation, those same thread groups  are  converted  to â
>           â"domain invalid" type.  What am I missing?           â
>           âââââââââââââââââââââââââââââââââââââââââââââââââââââââ

Yeah, I was confused with an earlier varient where we were marking
threaded domains instead of threaded roots.  It's mostly about future
extensibility (especially as Waiman was proposing related changes
there) and not doing things automatically / recursively if possible.

Looks good to me.

Thanks.

-- 
tejun