Re: [RFC][PATCH 6/7] sched: Balance RT tasks when forked as well

[Steven Rostedt <rostedt@goodmis.org>]

On Tue, 2011-07-26 at 14:36 +0200, Peter Zijlstra wrote:
> On Tue, 2011-07-26 at 08:35 -0400, Steven Rostedt wrote:
> > On Tue, 2011-07-26 at 14:25 +0200, Peter Zijlstra wrote:
> > > On Thu, 2011-06-16 at 21:55 -0400, Steven Rostedt wrote:
> > > > +       /* For anything but wake ups, just return the task_cpu */
> > > > +       if (sd_flag != SD_BALANCE_WAKE || sd_flag != SD_BALANCE_FORK) 
> > > 
> > > So we call select_task_rq() with SD_BALANCE_{WAKE,EXEC,FORK}, 
> > > 
> > > 	(WAKE != WAKE -> 0 || WAKE != FORK -> 1) -> 1
> > > 	(EXEC != WAKE -> 1 ) -> 1
> > > 	(FORK != WAKE -> 1 ) -> 1
> > > 
> > > IOW, you never end up doing anything now.. surely you didn't mean that?!
> > 
> > Bah!
> > 
> > s/||/&&/
> 
> So you only want to rebalance on EXEC? The comment says you want to
> balance on wakeups. Please as to unconfuse!?

The patch is (with fixup):

+       /* For anything but wake ups, just return the task_cpu */
+       if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
+               goto out;

In other words, if it isn't a WAKE or FORK (FORK being new task wakeup)
then exit the routine.

EXEC should not rebalance.

-- Steve