See the description of rfork at http://man.cat-v.org/plan_9/2/fork.

-rob


On Wed, Jun 3, 2020 at 9:21 AM Larry McVoy <lm@mcvoy.com> wrote:

> On Wed, Jun 03, 2020 at 09:09:08AM +1000, Rob Pike wrote:
> > The first mistake people made was to split "thread" from "process". What
> > those words mean today is not what they meant a generation ago.
>
> So I'm a fan of your quote, Rob, "If you think you need threads, your
> processes are too fat".
>
> Years ago, I asked Linus if he could fix the one flaw with that point
> of view.  Which is, processes can't share page tables.  So N processes
> will have N page tables, need an N way bigger TBL, to get the same
> performance.
>
> What I asked Linus to try and do is allow a process to share all or
> part of its page table with another process.  If that could be done,
> we could pretty do what you said, just use processes and if they want
> to act like threads, just share the page table.
>
> And I just looked, he seems to have done it.  man 2 clone on a
> Linux box.  It's the swiss army knife of features, feels messy.
>
> I don't know if CLONE_VM will share the page tables, I'll ask
> Linus.
>
> --lm
>