On Tue, 25 Jul 2006 10:53:39 +0900
KAMEZAWA Hiroyuki <[email protected]> wrote:
> On Mon, 24 Jul 2006 18:20:00 -0700
> Andrew Morton <[email protected]> wrote:
> >
> > It allocates a potentially-significant amount of memory per-task, until
> > that tasks exits (we could release it earlier, but the problem remains) and
> > it adds yet another global lock in the process exit path.
> >
> I see.
>
> > > 5 files changed, 138 insertions(+), 62 deletions(-)
> >
> > And it adds complexity and code.
> >
> > So I think we're still seeking a solution to this.
> >
> > Options might be:
> >
> > a) Pin the most-recently-visited task in some manner, so that it is
> > still on the global task list when we return. That's fairly simple to
> > do (defer the release_task()) but it affects task lifetime and visibility
> > in rare and worrisome ways.
> >
> > b) Change proc_pid_readdir() so that it walks the pid_hash[] array
> > instead of the task list. Need to do something clever when traversing
> > each bucket's list, but I'm not sure what ;) It's the same problem.
> >
> > Possibly what we could do here is to permit the task which is walking
> > /proc to pin a particular `struct pid': take a ref on it then when we
> > next start walking one of the pid_hash[] chains, we _know_ that the
> > `struct pid' which we're looking for will still be there. Even if it
> > now refers to a departed process.
> >
> > c) Nuke the pid_hash[], convert the whole thing to a radix-tree.
> > They're super-simple to traverse. Not sure what we'd index it by
> > though.
> >
> > I guess b) is best.
> >
>
> I tried b) at the first place.
OK.
> but it was not very good because
> proc_pid_readdir() has to traverse all pids, not tgids.
You mean "all tgids, not pids".
> So, I had to access
> task_struct of the pid. I wanted to avoid to access task struct itself,
Why do you wish to avoid accessing the task_struct?
> my patch implemented a table made only from tgids.
>
> But as you say, my patch is much intrusive.
> I'll dig this more. thank you for advise.
Thanks.
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