Messages in this thread | | | From | Pedro Alves <> | Subject | Re: [rfc 2/3] fs, proc: Introduce the Children: line in /proc/<pid>/status | Date | Fri, 2 Dec 2011 13:44:39 +0000 |
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On Friday 02 December 2011 13:16:52, Pavel Emelyanov wrote: > On 12/02/2011 04:58 PM, Pedro Alves wrote: > > On Friday 02 December 2011 12:43:10, Pavel Emelyanov wrote: > > > >>>> Yes, I like /children file. other points seems to be pointed out by other > >>>> reviewers. > >>> > >>> Any reason this is a file instead of a directory like /proc/PID/task/ ? > >>> > >>> $ sudo ls /proc/8167/task/ > >>> 8167 854 855 856 857 858 859 > >>> $ sudo ls /proc/8167/task/855/ > >>> attr clear_refs cpuset exe io loginuid mountinfo oom_adj pagemap sched smaps statm wchan > >>> auxv cmdline cwd fd latency maps mounts oom_score personality schedstat stack status > >>> cgroup comm environ fdinfo limits mem numa_maps oom_score_adj root sessionid stat syscall > >>> > >>> Much easier to follow the chain from the command line this way. > >> > >> What do you propose to put into these directories? Another directories named with > >> children pid-s? > > > > Yes, just like the task/ dir gives you directories named with the > > processes's thread ids. Opening /proc/PID/children/PID-CHILD1/ would get > > you the same as opening /proc/PID-CHILD1/. Just like > > opening /proc/PID/task/PID-CHILD1/ gets you (almost) the same as opening > > /proc/PID-CHILD1/. > > You cannot make the dentry named /proc/<pid1>/children/<pid2> be a hardlink on > the /proc/<pid2>. Thus you have to make arbitrary amount of inodes to point to > a single task. This brings unnecessary complexity and memory usage (by dentries > and proc inodes).
How is this different from the _already existing_ /proc/<pid1>/task/ directory? I can imagine that 98% of the code would be shared even? It's "just" a matter of listing thread group children (child/), instead of clone children (task/), isn't it?
They are not symbolic links under task/. /proc/<pid1>/task/<pid2>/ does not have a task/ subdir, only /proc/<pid1>/ does, I guess to avoid the memory usage issue you raise.
> I'd accept the symbolic links, but how would they look like? Like this: > # ls -l /proc/123/children > 234 -> ../../234 > ?
That'd work for me... but really, why not reuse tasks/'s code and behave the same?
-- Pedro Alves
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