[PATCH v2 5/9] drm/i915/gvt: factor out the scheduler

[Tian, Kevin]

> From: Ping Gao
> Sent: Tuesday, February 14, 2017 12:26 PM
> 
> Factor out the scheduler to a more clear structure, the basic logic
> is to find out next vGPU first and them schedule it. When decide to
> pick up who is the next vgpu it does split out two parts:
> first is to find a right sched head to keep fairness, second is to
> choose the vgpu has timeslice left.

the pick-up policy needs some elaboration.

> 
> Signed-off-by: Ping Gao <ping.a.gao at intel.com>
> ---
>  drivers/gpu/drm/i915/gvt/sched_policy.c | 73
> ++++++++++++++++++++++++---------
>  1 file changed, 54 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/sched_policy.c
> b/drivers/gpu/drm/i915/gvt/sched_policy.c
> index 6c53bf0..c174ce6 100644
> --- a/drivers/gpu/drm/i915/gvt/sched_policy.c
> +++ b/drivers/gpu/drm/i915/gvt/sched_policy.c
> @@ -118,28 +118,12 @@ static void try_to_schedule_next_vgpu(struct intel_gvt *gvt)
>  		wake_up(&scheduler->waitq[i]);
>  }
> 
> -#define GVT_DEFAULT_TIME_SLICE 1000000
> -
> -static void tbs_sched_func(struct tbs_sched_data *sched_data)
> +static struct intel_vgpu *get_vgpu_timeslice_left(struct list_head *head,
> +					struct tbs_sched_data *sched_data)
>  {

is it the right name? From the code comment, the remaining logic is
about finding a vGPU with pending workload...

>  	struct tbs_vgpu_data *vgpu_data;
> -
> -	struct intel_gvt *gvt = sched_data->gvt;
> -	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;
> -
>  	struct intel_vgpu *vgpu = NULL;
> -	struct list_head *pos, *head;
> -
> -	/* no vgpu or has already had a target */
> -	if (gvt->num_vgpu_sched <= 1 || scheduler->next_vgpu)
> -		goto out;
> -
> -	if (scheduler->current_vgpu) {
> -		vgpu_data = scheduler->current_vgpu->sched_data;
> -		head = &vgpu_data->list;
> -	} else {
> -		head = &sched_data->runq_head;
> -	}
> +	struct list_head *pos;
> 
>  	/* search a vgpu with pending workload */
>  	list_for_each(pos, head) {
> @@ -154,6 +138,57 @@ static void tbs_sched_func(struct tbs_sched_data *sched_data)
>  		break;
>  	}
> 
> +	return vgpu;
> +}
> +
> +static struct list_head *get_sched_head(struct tbs_sched_data *sched_data)
> +{
> +	struct intel_gvt *gvt = sched_data->gvt;
> +	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;
> +	struct tbs_vgpu_data *cur_vgpu_data;
> +	struct list_head *head;
> +
> +	if (scheduler->current_vgpu) {
> +		cur_vgpu_data = scheduler->current_vgpu->sched_data;
> +		head = &cur_vgpu_data->list;
> +	} else {
> +		gvt_dbg_sched("no current vgpu search from q head\n");
> +		head = &sched_data->runq_head;
> +	}
> +
> +	return head;
> +}

need a background somewhere e.g. how many sched queues we have now
and what's the purpose. otherwise not quite sure about the purpose here.

> +
> +static struct intel_vgpu *pickup_next_vgpu(struct tbs_sched_data *sched_data)
> +{
> +	struct intel_vgpu *next_vgpu = NULL;
> +	struct list_head *head = NULL;
> +
> +	/* The scheduler is follow round-robin style, sched
> +	 * head means where start to choose next vGPU, that's
> +	 * important to keep fairness. */
> +	head = get_sched_head(sched_data);
> +
> +	/* Choose the vGPU which has timeslice left */
> +	next_vgpu = get_vgpu_timeslice_left(head, sched_data);
> +
> +	return next_vgpu;
> +}
> +
> +#define GVT_DEFAULT_TIME_SLICE 1000000
> +
> +static void tbs_sched_func(struct tbs_sched_data *sched_data)
> +{
> +	struct intel_gvt *gvt = sched_data->gvt;
> +	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;
> +	struct intel_vgpu *vgpu = NULL;
> +
> +	/* no vgpu or has already had a target */
> +	if (gvt->num_vgpu_sched <= 1 || scheduler->next_vgpu)
> +		goto out;
> +
> +	/* determine which vGPU should choose as next */
> +	vgpu = pickup_next_vgpu(sched_data);
>  	if (vgpu) {
>  		scheduler->next_vgpu = vgpu;
>  		gvt_dbg_sched("pick next vgpu %d\n", vgpu->id);
> --
> 2.7.4
> 
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