Re: [patch 3/4] c/r: procfs: add arg_start/end, env_start/end and exit_code members to /proc/$pid/stat

[Cyrill Gorcunov <gorcunov@gmail.com>]

On Tue, Jan 24, 2012 at 03:59:41PM -0800, Andrew Morton wrote:
> On Mon, 23 Jan 2012 18:20:39 +0400
> Cyrill Gorcunov <gorcunov@openvz.org> wrote:
> 
> > We would like to have an ability to restore command line
> > arguments and envirion pointers so the task being restored
> > would print appropriate values in /proc/pid/cmdline and
> > /proc/pid/envirion. The exit_code is needed to restore
> > zombie tasks.
> > 
> 
> Please update Documentation/filesystems/proc.txt.

ok

> > +		(mm && permitted) ? mm->start_brk : 0,
> > +		(mm && permitted) ? mm->arg_start : 0,
> > +		(mm && permitted) ? mm->arg_end : 0,
> > +		(mm && permitted) ? mm->env_start : 0,
> > +		(mm && permitted) ? mm->env_end : 0,
> > +		task->exit_code);
> >  	if (mm)
> >  		mmput(mm);
> >  	return 0;
> 
> /proc/pid/stat is getting out of control.  People are now sending patches
> because reading from this thing already takes too long.
> 
> The problem is that if you only want one field, you have to incur the
> cost of preparing all the fields.  The magnitude of this problem
> increases exponentially over time!
> 
> I'm unsure what to do about it really.  Perhaps add a new
> /proc/pid/mmstat for MM-specific things.  We could put the above six
> fields in there, as long as we move quickly.
> 

I can add prctl PR_GET_MM with subcodes, since PR_SET_MM is already here
and wrapped with CHECKPOINT_RESTORE. Would this be better?

	Cyrill