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SubjectRe: [patch 3/4] c/r: procfs: add arg_start/end, env_start/end and exit_code members to /proc/$pid/stat
On Wed, 25 Jan 2012 10:54:50 +0400 Cyrill Gorcunov <gorcunov@gmail.com> wrote:

> > > + (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.

err, actually, that was /proc/stat/

> > 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?

mm, not really - /proc is the logical/expected place for it.

I'm thinking that perhaps we should start again with all of this and
export all this information in brand new, well-designed procfs files.
We'd still maintain /proc/stat and /proc/pid/stat but people should
migrate off them. Eventually (10 years?) everyone will be setting their
CONFIG_PROC_[PID_]STAT to 'n' and perhaps we can retire the things.

Meanwhile, I suppose you may as well continue to make /proc/pid/stat
even crazier :( It isn't as bad as /proc/stat!


btw, do we really need to do "(mm && permitted)" so many times? ie,
can we split that seq_printf up and do

if (mm && permitted) {
seq_printf(m + offset, "%lu", mm->start_data);
...
} else {
seq_printf(m + offset, "0 0 0 0 0 0 0 0 0");
}

? Although this probably won't help much.


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