From: Dario Faggioli <dario.faggioli@citrix.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: xen-devel@lists.xenproject.org,
Anshul Makkar <anshul.makkar@citrix.com>,
David Vrabel <david.vrabel@citrix.com>,
George Dunlap <george.dunlap@citrix.com>
Subject: Re: [PATCH 01/19] xen: sched: leave CPUs doing tasklet work alone.
Date: Thu, 7 Jul 2016 12:11:52 +0200 [thread overview]
Message-ID: <1467886312.23985.41.camel@citrix.com> (raw)
In-Reply-To: <5767BBED02000078000F67D0@prv-mh.provo.novell.com>
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On Mon, 2016-06-20 at 01:48 -0600, Jan Beulich wrote:
> > > > On 18.06.16 at 01:11, <dario.faggioli@citrix.com> wrote:
> > --- a/xen/common/sched_credit.c
> > +++ b/xen/common/sched_credit.c
> > @@ -1819,24 +1819,24 @@ csched_schedule(
> > else
> > snext = csched_load_balance(prv, cpu, snext,
> > &ret.migrated);
> >
> > + out:
> > /*
> > * Update idlers mask if necessary. When we're idling, other
> > CPUs
> > * will tickle us when they get extra work.
> > */
> > - if ( snext->pri == CSCHED_PRI_IDLE )
> > + if ( tasklet_work_scheduled || snext->pri != CSCHED_PRI_IDLE )
> > {
> > - if ( !cpumask_test_cpu(cpu, prv->idlers) )
> > - cpumask_set_cpu(cpu, prv->idlers);
> > + if ( cpumask_test_cpu(cpu, prv->idlers) )
> > + cpumask_clear_cpu(cpu, prv->idlers);
> > }
> > - else if ( cpumask_test_cpu(cpu, prv->idlers) )
> > + else if ( !cpumask_test_cpu(cpu, prv->idlers) )
> > {
> > - cpumask_clear_cpu(cpu, prv->idlers);
> > + cpumask_set_cpu(cpu, prv->idlers);
> > }
> Is there a reason for this extra code churn? It would seem to me
> that the change could be just the "out" label movement and
> adjustment to the first if:
>
> if ( !tasklet_work_scheduled && snext->pri == CSCHED_PRI_IDLE )
>
> Am I overlooking something?
>
No, you are not. It indeed can be done as you suggest, and it's better,
so I'll go for it.
Thanks and regards,
Dario
--
<<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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next prev parent reply other threads:[~2016-07-07 10:11 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-17 23:11 [PATCH 00/19] xen: sched: assorted fixes and improvements to Credit2 Dario Faggioli
2016-06-17 23:11 ` [PATCH 01/19] xen: sched: leave CPUs doing tasklet work alone Dario Faggioli
2016-06-20 7:48 ` Jan Beulich
2016-07-07 10:11 ` Dario Faggioli [this message]
2016-06-21 16:17 ` anshul makkar
2016-07-06 15:41 ` George Dunlap
2016-07-07 10:25 ` Dario Faggioli
2016-06-17 23:11 ` [PATCH 02/19] xen: sched: make the 'tickled' perf counter clearer Dario Faggioli
2016-06-18 0:36 ` Meng Xu
2016-07-06 15:52 ` George Dunlap
2016-06-17 23:11 ` [PATCH 03/19] xen: credit2: insert and tickle don't need a cpu parameter Dario Faggioli
2016-06-21 16:41 ` anshul makkar
2016-07-06 15:59 ` George Dunlap
2016-06-17 23:11 ` [PATCH 04/19] xen: credit2: kill useless helper function choose_cpu Dario Faggioli
2016-07-06 16:02 ` George Dunlap
2016-07-07 10:26 ` Dario Faggioli
2016-06-17 23:11 ` [PATCH 05/19] xen: credit2: do not warn if calling burn_credits more than once Dario Faggioli
2016-07-06 16:05 ` George Dunlap
2016-06-17 23:12 ` [PATCH 06/19] xen: credit2: read NOW() with the proper runq lock held Dario Faggioli
2016-06-20 7:56 ` Jan Beulich
2016-07-06 16:10 ` George Dunlap
2016-07-07 10:28 ` Dario Faggioli
2016-06-17 23:12 ` [PATCH 07/19] xen: credit2: prevent load balancing to go mad if time goes backwards Dario Faggioli
2016-06-20 8:02 ` Jan Beulich
2016-07-06 16:21 ` George Dunlap
2016-07-07 7:29 ` Jan Beulich
2016-07-07 9:09 ` George Dunlap
2016-07-07 9:18 ` Jan Beulich
2016-07-07 10:53 ` Dario Faggioli
2016-06-17 23:12 ` [PATCH 08/19] xen: credit2: when tickling, check idle cpus first Dario Faggioli
2016-07-06 16:36 ` George Dunlap
2016-06-17 23:12 ` [PATCH 09/19] xen: credit2: avoid calling __update_svc_load() multiple times on the same vcpu Dario Faggioli
2016-07-06 16:40 ` George Dunlap
2016-06-17 23:12 ` [PATCH 10/19] xen: credit2: rework load tracking logic Dario Faggioli
2016-07-06 17:33 ` George Dunlap
2016-06-17 23:12 ` [PATCH 11/19] tools: tracing: adapt Credit2 load tracking events to new format Dario Faggioli
2016-06-21 9:27 ` Wei Liu
2016-06-17 23:12 ` [PATCH 12/19] xen: credit2: use non-atomic cpumask and bit operations Dario Faggioli
2016-07-07 9:45 ` George Dunlap
2016-06-17 23:12 ` [PATCH 13/19] xen: credit2: make the code less experimental Dario Faggioli
2016-06-20 8:13 ` Jan Beulich
2016-07-07 10:59 ` Dario Faggioli
2016-07-07 15:17 ` George Dunlap
2016-07-07 16:43 ` Dario Faggioli
2016-06-17 23:12 ` [PATCH 14/19] xen: credit2: add yet some more tracing Dario Faggioli
2016-06-20 8:15 ` Jan Beulich
2016-07-07 15:34 ` George Dunlap
2016-07-07 15:34 ` George Dunlap
2016-06-17 23:13 ` [PATCH 15/19] xen: credit2: only marshall trace point arguments if tracing enabled Dario Faggioli
2016-07-07 15:37 ` George Dunlap
2016-06-17 23:13 ` [PATCH 16/19] tools: tracing: deal with new Credit2 events Dario Faggioli
2016-07-07 15:39 ` George Dunlap
2016-06-17 23:13 ` [PATCH 17/19] xen: credit2: the private scheduler lock can be an rwlock Dario Faggioli
2016-07-07 16:00 ` George Dunlap
2016-06-17 23:13 ` [PATCH 18/19] xen: credit2: implement SMT support independent runq arrangement Dario Faggioli
2016-06-20 8:26 ` Jan Beulich
2016-06-20 10:38 ` Dario Faggioli
2016-06-27 15:20 ` anshul makkar
2016-07-12 13:40 ` George Dunlap
2016-06-17 23:13 ` [PATCH 19/19] xen: credit2: use cpumask_first instead of cpumask_any when choosing cpu Dario Faggioli
2016-06-20 8:30 ` Jan Beulich
2016-06-20 11:28 ` Dario Faggioli
2016-06-21 10:42 ` David Vrabel
2016-07-07 16:55 ` Dario Faggioli
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