From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dario Faggioli <dario.faggioli@citrix.com>
Subject: Re: [PATCH v6 for Xen 4.7 1/4] xen: enable per-VCPU
 parameter settings for RTDS scheduler
Date: Wed, 9 Mar 2016 17:10:04 +0100
Message-ID: <1457539804.3102.425.camel@citrix.com>
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To: Wei Liu <wei.liu2@citrix.com>, Chong Li <lichong659@gmail.com>
Cc: Chong Li <chong.li@wustl.edu>, Sisu Xi <xisisu@gmail.com>, george.dunlap@eu.citrix.com, xen-devel@lists.xen.org, Meng Xu <mengxu@cis.upenn.edu>, jbeulich@suse.com, dgolomb@seas.upenn.edu
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On Tue, 2016-03-08 at 19:09 +0000, Wei Liu wrote:
> On Sun, Mar 06, 2016 at 11:55:55AM -0600, Chong Li wrote:
>=C2=A0
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0spin_lock_irqsave(&prv->lock, flags);
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0svc =3D rt_vcpu(d->vcpu[local_sched.vcpuid]);
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0svc->period =3D period;
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0svc->budget =3D budget;
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0spin_unlock_irqrestore(&prv->lock, flags);
> > +
> And this locking pattern seems sub-optimal. You might be able to move
> the lock and unlock outside the while loop?
>=20
Yes, unless I'm missing something, that looks possible to me, and would
save a lot of acquire/release ping pong on the lock.

And yet, I'm not sure doing (for large guests) batches of 64 iterations
with (as of now) interrupts disabled.

I'll think about this...

Thanks and Regards,
Dario
--=20
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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