Re: [GIT PULL] First batch of KVM changes for 4.1

Peter Zijlstra
2015-04-17T10:37:14Z

On Fri, Apr 17, 2015 at 12:09:49PM +0200, Paolo Bonzini wrote:
>
>
> On 17/04/2015 11:17, Peter Zijlstra wrote:
> > On Fri, Apr 17, 2015 at 10:52:38AM +0200, Peter Zijlstra wrote:
> >> On Fri, Apr 10, 2015 at 05:01:29PM +0200, Paolo Bonzini wrote:
> >>> include/linux/sched.h | 8 +
> >>> kernel/sched/core.c | 15 +
> >>
> >> Can you please not puke over the scheduler without Acks from at least
> >> one maintainer?
>
> Sorry, this was done while I was not handling the KVM tree. At the very
> least the commit message should have included the original hashes of the
> commit and the revert. This way one could have found the original Acks:
>
> commit 582b336ec2c0f0076f5650a029fcc9abd4a906f7
> Author: Marcelo Tosatti <mtosatti@redhat.com>
> Date: Tue Nov 27 23:28:54 2012 -0200
>
> sched: add notifier for cross-cpu migrations
>
> Originally from Jeremy Fitzhardinge.
>
> Acked-by: Ingo Molnar <mingo@redhat.com>
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Still not a good reason to sneak it back it now, after I got it taken
out. There was a reason it was removed, prior acks (esp. 2 year old
ones) do not count one whit _NOW_.

Also, Ingo later agreed that is was a mistake,

http://marc.info/?l=linux-kernel&m=137346715521978&w=2

which is an effective retract of whatever ACK that was.

It was crap code then and its crap code now.

> >> I complained about this very thing two years ago:
> >>
> >> http://marc.info/?l=linux-kernel&m=137345253916751
> >>
> >> And now it magically re-appears WTF!
> >
> > And I really don't understand _why_ you need that extra callback in the
> > first place. You already have preempt notifiers, just track if you came
> > in on another cpu than you went out on and voila!
>
> Then you pay for _all_ preemptions of _all_ processes in the guest,
> instead of the hopefully rare ones that do a CPU migration.

Now you make everybody pay for your crap, x86-64 paravirt or not. Keep
the cost by those who need it.

Please take it out, ASAP.