Re: [Xen-devel] [RFC/RFT][PATCH 0 of 3] rework locking in sched_adjust

[Dario Faggioli <raistlin@xxxxxxxx>]

On Tue, Dec 6, 2011 at 1:24 PM, George Dunlap
<George.Dunlap@xxxxxxxxxxxxx> wrote:
> Hey Dario,  sorry for the long delay in responding.
>
Hi, and no problem at all :-)

> Regressions in mid-patch series are bad because it can mess up bisection.
>
I strongly agree. I didn't think much about that for this series since
the mechanism
I was trying to fix was (especially for sedf) already broken in
various ways but,
indeed, patches could be better split.

> I think a better way of breaking it down would be:
> * Add scheduler global locks, and have them called in the pluggable
> scheduler *_adjust() function.  This is redundant, but shouldn't be
> harmful.
> * Atomically remove both the pause and the lock in schedule.c, and add
> the scheduling locks around the per-vcpu EDOM_INFO variables in
> sched_sedf.c, all in one patch.  This makes the patch bigger, but it
> avoids a regression.
>
Ok, I'll go for this.

> The two things are related anwyay: the reason
> you now need scheduling locks around EDOM_INFO variables is because
> you're getting rid of the pausing and the lock in schedule.c.
>
Yeah, what I was trying to do was leaving a clear footstep about why
pausing was going and, yes, also making patches smaller, but again, I
see your point and will follow your advice. :-)

Thanks and Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
----------------------------------------------------------------------
Dario Faggioli, http://retis.sssup.it/people/faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)
PhD Candidate, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa  (Italy)

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