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From: George Dunlap <george.dunlap@citrix.com>
To: Dario Faggioli <dario.faggioli@citrix.com>,
	xen-devel@lists.xenproject.org
Cc: George Dunlap <george.dunlap@eu.citrix.com>,
	Justin Weaver <jtweaver@hawaii.edu>
Subject: Re: [PATCH 12/16] xen: sched: fix per-socket runqueue creation in credit2
Date: Thu, 24 Mar 2016 12:24:43 +0000	[thread overview]
Message-ID: <56F3DC8B.10703@citrix.com> (raw)
In-Reply-To: <20160318190530.8117.62203.stgit@Solace.station>

On 18/03/16 19:05, Dario Faggioli wrote:
> The credit2 scheduler tries to setup runqueues in such
> a way that there is one of them per each socket. However,
> that does not work. The issue is described in bug #36
> "credit2 only uses one runqueue instead of one runq per
> socket" (http://bugs.xenproject.org/xen/bug/36), and a
> solution has been attempted by an old patch series:
> 
>  http://lists.xen.org/archives/html/xen-devel/2014-08/msg02168.html
> 
> Here, we take advantage of the fact that now initialization
> happens (for all schedulers) during CPU_STARTING, so we
> have all the topology information available when necessary.
> 
> This is true for all the pCPUs _except_ the boot CPU. That
> is not an issue, though. In fact, no runqueue exists yet
> when the boot CPU is initialized, so we can just create
> one and put the boot CPU in there.

The loop is a genius idea, Dario! Well done.

One minor nit...

> Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
> ---
> Cc: George Dunlap <george.dunlap@eu.citrix.com>
> Cc: Justin Weaver <jtweaver@hawaii.edu>
> ---
>  xen/common/sched_credit2.c |   59 ++++++++++++++++++++++++++++++++------------
>  1 file changed, 43 insertions(+), 16 deletions(-)
> 
> diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
> index 4ff26c9..456b9ea 100644
> --- a/xen/common/sched_credit2.c
> +++ b/xen/common/sched_credit2.c
> @@ -53,7 +53,6 @@
>   *  http://wiki.xen.org/wiki/Credit2_Scheduler_Development
>   * TODO:
>   * + Multiple sockets
> - *  - Detect cpu layout and make runqueue map, one per L2 (make_runq_map())
>   *  - Simple load balancer / runqueue assignment
>   *  - Runqueue load measurement
>   *  - Load-based load balancer
> @@ -1972,6 +1971,48 @@ static void deactivate_runqueue(struct csched2_private *prv, int rqi)
>      cpumask_clear_cpu(rqi, &prv->active_queues);
>  }
>  
> +static unsigned int
> +cpu_to_runqueue(struct csched2_private *prv, unsigned int cpu)
> +{
> +    struct csched2_runqueue_data *rqd;
> +    unsigned int rqi;
> +
> +    for ( rqi = 0; rqi < nr_cpu_ids; rqi++ )
> +    {
> +        unsigned int peer_cpu;
> +
> +        /*
> +         * As soon as we come across an uninitialized runqueue, use it.
> +         * In fact, either:
> +         *  - we are initializing the first cpu, and we assign it to
> +         *    runqueue 0. This is handy, especially if we are dealing
> +         *    with the boot cpu (if credit2 is the default scheduler),
> +         *    as we would not be able to use cpu_to_socket() and similar
> +         *    helpers anyway (they're result of which is not reliable yet);
> +         *  - we have gone through all the active runqueues, and have not
> +         *    found anyone whose cpus' topology matches the one we are
> +         *    dealing with, so ativating a new runqueue is what we want.
> +         */

*activating

With that fixed:

Reviewed-by: George Dunlap <george.dunlap@citrix.com>


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  reply	other threads:[~2016-03-24 12:24 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 [this message]
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
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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