Re: [REPORT] cfs-v4 vs sd-0.44

Willy Tarreau
2007-04-21T16:55:20Z

On Sat, Apr 21, 2007 at 09:34:07AM -0700, Linus Torvalds wrote:
>
>
> On Sat, 21 Apr 2007, Willy Tarreau wrote:
> >
> > If you remember, with 50/50, I noticed some difficulties to fork many
> > processes. I think that during a fork(), the parent has a higher probability
> > of forking other processes than the child. So at least, we should use
> > something like 67/33 or 75/25 for parent/child.
>
> It would be even better to simply have the rule:
> - child gets almost no points at startup
> - but when a parent does a "waitpid()" call and blocks, it will spread
> out its points to the childred (the "vfork()" blocking is another case
> that is really the same).
>
> This is a very special kind of "priority inversion" logic: you give higher
> priority to the things you wait for. Not because of holding any locks, but
> simply because a blockign waitpid really is a damn big hint that "ok, the
> child now works for the parent".

I like this idea a lot. I don't know if it can be applied to pipes and unix
sockets, but it's clearly a way of saying "hurry up, I'm waiting for you"
which seems natural with inter-process communications. Also, if we can do
this on unix sockets, it would help a lot with X !

Willy