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From: Dario Faggioli <dfaggioli@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
	xen-devel@lists.xenproject.org
Cc: George Dunlap <george.dunlap@eu.citrix.com>
Subject: Re: [PATCH 1/2] xen: credit2: avoid using cpumask_weight() in hot-paths
Date: Fri, 26 Apr 2019 15:01:15 +0200	[thread overview]
Message-ID: <49b2fb80a576cff4b26ae09668cc8b5b243a9f9a.camel@suse.com> (raw)
In-Reply-To: <c7f0e1c1-f69f-3c53-7147-21e24d4618b1@citrix.com>


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On Tue, 2019-04-23 at 10:44 +0100, Andrew Cooper wrote:
> On 20/04/2019 16:24, Dario Faggioli wrote:
>
> Definitely +1 to algorithm changes which avoid its use entirely.
> 
> A few cosmetic observations.
> 
Ok...

> > diff --git a/xen/common/sched_credit2.c
> > b/xen/common/sched_credit2.c
> > index 6958b265fc..7034325243 100644
> > --- a/xen/common/sched_credit2.c
> > +++ b/xen/common/sched_credit2.c
> > @@ -466,6 +466,7 @@ struct csched2_runqueue_data {
> >      spinlock_t lock;           /* Lock for this
> > runqueue                     */
> >  
> >      struct list_head runq;     /* Ordered list of runnable
> > vms               */
> > +    int nr_cpus;               /* How many CPUs are sharing this
> > runqueue    */
> 
> Unsigned int.
> 
Yep.

> > @@ -3944,8 +3951,12 @@ csched2_deinit_pdata(const struct scheduler
> > *ops, void *pcpu, int cpu)
> >      __cpumask_clear_cpu(cpu, &rqd->smt_idle);
> >      __cpumask_clear_cpu(cpu, &rqd->active);
> >  
> > -    if ( cpumask_empty(&rqd->active) )
> > +    rqd->nr_cpus--;
> > +    ASSERT(cpumask_weight(&rqd->active) == rqd->nr_cpus);
> > +
> > +    if ( rqd->nr_cpus == 0 )
> >      {
> > +	ASSERT(cpumask_empty(&rqd->active));
> 
> And here.
> 
Right. Not sure how they ended in there. Will remove them.

> Is it really worth having both asserts?  The second is redundant.
> 
I think I agree. I'll keep the first one only.

Thanks and Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
-------------------------------------------------------------------
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)


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_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

WARNING: multiple messages have this Message-ID (diff)
From: Dario Faggioli <dfaggioli@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
	xen-devel@lists.xenproject.org
Cc: George Dunlap <george.dunlap@eu.citrix.com>
Subject: Re: [Xen-devel] [PATCH 1/2] xen: credit2: avoid using cpumask_weight() in hot-paths
Date: Fri, 26 Apr 2019 15:01:15 +0200	[thread overview]
Message-ID: <49b2fb80a576cff4b26ae09668cc8b5b243a9f9a.camel@suse.com> (raw)
Message-ID: <20190426130115.jKP46pnAXxSXtof-pAmAq1iATcFRwnYVSqDn-_tNUWM@z> (raw)
In-Reply-To: <c7f0e1c1-f69f-3c53-7147-21e24d4618b1@citrix.com>


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On Tue, 2019-04-23 at 10:44 +0100, Andrew Cooper wrote:
> On 20/04/2019 16:24, Dario Faggioli wrote:
>
> Definitely +1 to algorithm changes which avoid its use entirely.
> 
> A few cosmetic observations.
> 
Ok...

> > diff --git a/xen/common/sched_credit2.c
> > b/xen/common/sched_credit2.c
> > index 6958b265fc..7034325243 100644
> > --- a/xen/common/sched_credit2.c
> > +++ b/xen/common/sched_credit2.c
> > @@ -466,6 +466,7 @@ struct csched2_runqueue_data {
> >      spinlock_t lock;           /* Lock for this
> > runqueue                     */
> >  
> >      struct list_head runq;     /* Ordered list of runnable
> > vms               */
> > +    int nr_cpus;               /* How many CPUs are sharing this
> > runqueue    */
> 
> Unsigned int.
> 
Yep.

> > @@ -3944,8 +3951,12 @@ csched2_deinit_pdata(const struct scheduler
> > *ops, void *pcpu, int cpu)
> >      __cpumask_clear_cpu(cpu, &rqd->smt_idle);
> >      __cpumask_clear_cpu(cpu, &rqd->active);
> >  
> > -    if ( cpumask_empty(&rqd->active) )
> > +    rqd->nr_cpus--;
> > +    ASSERT(cpumask_weight(&rqd->active) == rqd->nr_cpus);
> > +
> > +    if ( rqd->nr_cpus == 0 )
> >      {
> > +	ASSERT(cpumask_empty(&rqd->active));
> 
> And here.
> 
Right. Not sure how they ended in there. Will remove them.

> Is it really worth having both asserts?  The second is redundant.
> 
I think I agree. I'll keep the first one only.

Thanks and Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
-------------------------------------------------------------------
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)


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_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

  reply	other threads:[~2019-04-26 13:01 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-20 15:24 [PATCH 0/2] xen: sched/Credit2: small and trivial improvements Dario Faggioli
2019-04-20 15:24 ` [Xen-devel] " Dario Faggioli
2019-04-20 15:24 ` [PATCH 1/2] xen: credit2: avoid using cpumask_weight() in hot-paths Dario Faggioli
2019-04-20 15:24   ` [Xen-devel] " Dario Faggioli
2019-04-23  9:44   ` Andrew Cooper
2019-04-23  9:44     ` [Xen-devel] " Andrew Cooper
2019-04-26 13:01     ` Dario Faggioli [this message]
2019-04-26 13:01       ` Dario Faggioli
2019-04-23  9:48   ` Andrii Anisov
2019-04-23  9:48     ` [Xen-devel] " Andrii Anisov
2019-04-20 15:24 ` [PATCH 2/2] xen: sched: we never get into context_switch() with prev==next Dario Faggioli
2019-04-20 15:24   ` [Xen-devel] " Dario Faggioli
2019-04-21 17:08   ` Julien Grall
2019-04-21 17:08     ` [Xen-devel] " Julien Grall
2019-04-23  9:13   ` Andrii Anisov
2019-04-23  9:13     ` [Xen-devel] " Andrii Anisov
2019-04-23  9:47     ` Andrew Cooper
2019-04-23  9:47       ` [Xen-devel] " Andrew Cooper
2019-04-23 10:33       ` Andrii Anisov
2019-04-23 10:33         ` [Xen-devel] " Andrii Anisov
2019-04-26 15:13     ` Dario Faggioli
2019-04-26 15:13       ` [Xen-devel] " Dario Faggioli
2019-04-26 16:22       ` Julien Grall
2019-04-26 16:22         ` [Xen-devel] " Julien Grall
2019-04-26 16:26         ` Andrew Cooper
2019-04-26 16:26           ` [Xen-devel] " Andrew Cooper
2019-05-08 10:03       ` Andrii Anisov
2019-05-08 10:03         ` [Xen-devel] " Andrii Anisov
2019-04-23  9:50   ` George Dunlap
2019-04-23  9:50     ` [Xen-devel] " George Dunlap
2019-04-23  9:56     ` Juergen Gross
2019-04-23  9:56       ` [Xen-devel] " Juergen Gross
2019-04-26 12:58       ` Dario Faggioli
2019-04-26 12:58         ` [Xen-devel] " Dario Faggioli
2019-04-23 10:00   ` Andrew Cooper
2019-04-23 10:00     ` [Xen-devel] " Andrew Cooper

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