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From: George Dunlap <george.dunlap@citrix.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
	Dario Faggioli <dario.faggioli@citrix.com>,
	xen-devel@lists.xenproject.org
Cc: George Dunlap <george.dunlap@eu.citrix.com>
Subject: Re: [PATCH 15/16] xen: sched: scratch space for cpumasks on Credit2
Date: Thu, 24 Mar 2016 12:44:19 +0000	[thread overview]
Message-ID: <56F3E123.7030808@citrix.com> (raw)
In-Reply-To: <56EC56B1.7040907@citrix.com>

On 18/03/16 19:27, Andrew Cooper wrote:
> On 18/03/16 19:06, Dario Faggioli wrote:
>> like what's there already in both Credit1 and RTDS. In
>> fact, when playing with affinity, a lot of cpumask
>> manipulation is necessary, inside of various functions.
>>
>> To avoid having a lot of cpumask_var_t on the stack,
>> this patch introduces a global scratch area.
>>
>> Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
>> ---
>> Cc: George Dunlap <george.dunlap@eu.citrix.com>
>> ---
> 
> I would suggest instead going with
> 
> static DEFINE_PER_CPU(cpumask_t, csched2_cpumask_scratch);
> 
> Functions which want to use it can use
> 
> cpumask_t *scratch = &this_cpu(csched2_cpumask_scratch);
> 
> 
> This avoids all this opencoded allocation/refcounting, the chance that
> starting a scheduler would fail for memory reasons, and one extra
> cpumask in the per-cpu data area won't break the bank.

Going a bit further, since (according to the changelog) both credit1 and
rtds also do this, would it make sense to have schedule.c define these,
and allow any of the schedulers to use them?

(Assuming that both credit1 and rtds allocate exactly one mask per cpu.)

 -George


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  reply	other threads:[~2016-03-24 12:44 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-18 19:03 [PATCH 00/16] Fixes and improvement (including hard affinity!) for Credit2 Dario Faggioli
2016-03-18 19:04 ` [PATCH 01/16] xen: sched: fix locking when allocating an RTDS pCPU Dario Faggioli
2016-03-19  2:22   ` Meng Xu
2016-03-23 15:37   ` George Dunlap
2016-03-18 19:04 ` [PATCH 02/16] xen: sched: add .init_pdata hook to the scheduler interface Dario Faggioli
2016-03-22  8:08   ` Juergen Gross
2016-03-23 17:32   ` George Dunlap
2016-03-18 19:04 ` [PATCH 03/16] xen: sched: make implementing .alloc_pdata optional Dario Faggioli
2016-03-19  2:23   ` Meng Xu
2016-03-21 14:22   ` Jan Beulich
2016-03-23 17:36     ` George Dunlap
2016-03-24  9:43       ` Jan Beulich
2016-03-24 13:14         ` Dario Faggioli
2016-03-21 14:48   ` Juergen Gross
2016-03-21 15:07     ` Jan Beulich
2016-04-01 17:01       ` Dario Faggioli
2016-04-04  4:21         ` Juergen Gross
2016-04-04  6:13         ` Jan Beulich
2016-04-05 16:01           ` Dario Faggioli
2016-03-23 17:38   ` George Dunlap
2016-03-18 19:04 ` [PATCH 04/16] xen: sched: implement .init_pdata in all schedulers Dario Faggioli
2016-03-19  2:24   ` Meng Xu
2016-03-22  8:03   ` Juergen Gross
2016-03-23 17:46     ` George Dunlap
2016-03-18 19:04 ` [PATCH 05/16] xen: sched: move pCPU initialization in an helper Dario Faggioli
2016-03-23 17:51   ` George Dunlap
2016-03-23 18:09     ` George Dunlap
2016-03-24 13:21     ` Dario Faggioli
2016-03-18 19:04 ` [PATCH 06/16] xen: sched: prepare a .switch_sched hook for Credit1 Dario Faggioli
2016-03-18 19:04 ` [PATCH 07/16] xen: sched: prepare a .switch_sched hook for Credit2 Dario Faggioli
2016-03-18 19:04 ` [PATCH 08/16] " Dario Faggioli
2016-03-19  2:24   ` Meng Xu
2016-03-21 14:25   ` Jan Beulich
2016-03-18 19:05 ` [PATCH 09/16] xen: sched: close potential races when switching scheduler to CPUs Dario Faggioli
2016-03-19  2:25   ` Meng Xu
2016-03-23 19:05   ` George Dunlap
2016-04-05 16:26     ` Dario Faggioli
2016-04-06 15:51       ` Dario Faggioli
2016-03-24 12:14   ` George Dunlap
2016-04-05 17:37     ` Dario Faggioli
2016-04-06 16:21       ` Dario Faggioli
2016-03-18 19:05 ` [PATCH 10/16] xen: sched: improve credit2 bootparams' scope, placement and signedness Dario Faggioli
2016-03-21 14:51   ` Juergen Gross
2016-03-24 12:20   ` George Dunlap
2016-03-18 19:05 ` [PATCH 11/16] xen: sched: on Credit2, don't reprogram the timer if idle Dario Faggioli
2016-03-24 15:03   ` George Dunlap
2016-03-18 19:05 ` [PATCH 12/16] xen: sched: fix per-socket runqueue creation in credit2 Dario Faggioli
2016-03-24 12:24   ` George Dunlap
2016-03-18 19:05 ` [PATCH 13/16] xen: sched: allow for choosing credit2 runqueues configuration at boot Dario Faggioli
2016-03-22  7:46   ` Juergen Gross
2016-03-24 12:36   ` George Dunlap
2016-03-18 19:05 ` [PATCH 14/16] xen: sched: per-core runqueues as default in credit2 Dario Faggioli
2016-03-24 12:37   ` George Dunlap
2016-03-18 19:06 ` [PATCH 15/16] xen: sched: scratch space for cpumasks on Credit2 Dario Faggioli
2016-03-18 19:27   ` Andrew Cooper
2016-03-24 12:44     ` George Dunlap [this message]
2016-03-24 12:56       ` Andrew Cooper
2016-03-24 13:10       ` Dario Faggioli
2016-03-18 19:06 ` [PATCH 16/16] xen: sched: implement vcpu hard affinity in Credit2 Dario Faggioli
2016-03-24 15:42   ` George Dunlap
2016-04-05 16:50     ` Dario Faggioli

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