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

William Lee Irwin III
2007-04-21T16:46:42Z

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.

On Sat, Apr 21, 2007 at 09:34:07AM -0700, Linus Torvalds wrote:
> 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".

An in-kernel scheduler API might help. void yield_to(struct task_struct *)?

A userspace API might be nice, too. e.g. int sched_yield_to(pid_t).

-- wli