Re: [patch] CFS scheduler, -v8

[Bill Huey (hui) <billh@gnuppy.monkey.org>]

On Wed, May 02, 2007 at 11:18:45PM -0400, Ting Yang wrote:
> I just want to point out that ->wait_runtime, in fact, stores the lag of 
> each task in CFS, except that it is also used by other things, and 
> occasionally tweaked (heuristically ?). Under normal cases the sum of 
> lags of all active tasks in such a system, should be a constant 0. The 
> lag information is equally important to EEVDF, when some tasks leave the 
> system (becomes inactive) carrying certain amount of lag. The key point 
> here is that we have to spread the lag (either negative or positive) to 
> all remaining task, so that the fairness of the system is preserved. I 
> thinks CFS implementation does not seems to handle this properly.
> 
> I am running out time today :-( I will write an email about CFS -v8 
> tomorrow, describing 2 issues in CFS I found related to this.

Interesting. I haven't look at the code carefully but that wouldn't
surprise me if this was the case and it led to odd corner cases.

I'm eagerly waiting your analysis and explanation.

bill