[PATCH v2] drm/i915/gvt: Give new born vGPU higher scheduling chance

[Yuan, Hang]

Thanks for the patch! I did a quick test to simulate 2s delay in Windows guest's workload execution and don't find any GPU hang or windows reboot.

Reviewed-by: Hang Yuan <hang.yuan at intel.com>

> -----Original Message-----
> From: Zhenyu Wang [mailto:zhenyuw at linux.intel.com]
> Sent: Thursday, August 30, 2018 11:34 AM
> To: intel-gvt-dev at lists.freedesktop.org
> Cc: Yuan, Hang <hang.yuan at intel.com>
> Subject: [PATCH v2] drm/i915/gvt: Give new born vGPU higher scheduling
> chance
> 
> This trys to give new born vGPU with higher scheduling chance not only with
> adding to sched list head and also have higher priority for workload sched for
> 2 seconds after starting to schedule it. In order for fast GPU execution during
> VM boot, and ensure guest driver setup with required state given in time.
> 
> This fixes recent failure seen on one VM with multiple linux VMs running on
> kernel with commit 2621cefaa42b3("drm/i915: Provide a timeout to
> i915_gem_wait_for_idle() on setup"), which had shorter setup timeout that
> caused context state init failed.
> 
> v2: change to 2s for higher scheduling period
> 
> Cc: Yuan Hang <hang.yuan at intel.com>
> Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/gvt/sched_policy.c | 34 ++++++++++++++++++++-----
>  1 file changed, 27 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/sched_policy.c
> b/drivers/gpu/drm/i915/gvt/sched_policy.c
> index 09d7bb72b4ff..514e075f74a7 100644
> --- a/drivers/gpu/drm/i915/gvt/sched_policy.c
> +++ b/drivers/gpu/drm/i915/gvt/sched_policy.c
> @@ -47,11 +47,15 @@ static bool vgpu_has_pending_workload(struct
> intel_vgpu *vgpu)
>  	return false;
>  }
> 
> +/* We give 2 seconds higher prio for vGPU during start */ #define
> +GVT_SCHED_VGPU_PRI_TIME  2
> +
>  struct vgpu_sched_data {
>  	struct list_head lru_list;
>  	struct intel_vgpu *vgpu;
>  	bool active;
> -
> +	bool pri_sched;
> +	ktime_t pri_time;
>  	ktime_t sched_in_time;
>  	ktime_t sched_time;
>  	ktime_t left_ts;
> @@ -183,6 +187,14 @@ static struct intel_vgpu *find_busy_vgpu(struct
> gvt_sched_data *sched_data)
>  		if (!vgpu_has_pending_workload(vgpu_data->vgpu))
>  			continue;
> 
> +		if (vgpu_data->pri_sched) {
> +			if (ktime_before(ktime_get(), vgpu_data->pri_time)) {
> +				vgpu = vgpu_data->vgpu;
> +				break;
> +			} else
> +				vgpu_data->pri_sched = false;
> +		}
> +
>  		/* Return the vGPU only if it has time slice left */
>  		if (vgpu_data->left_ts > 0) {
>  			vgpu = vgpu_data->vgpu;
> @@ -202,6 +214,7 @@ static void tbs_sched_func(struct gvt_sched_data
> *sched_data)
>  	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;
>  	struct vgpu_sched_data *vgpu_data;
>  	struct intel_vgpu *vgpu = NULL;
> +
>  	/* no active vgpu or has already had a target */
>  	if (list_empty(&sched_data->lru_runq_head) || scheduler-
> >next_vgpu)
>  		goto out;
> @@ -209,12 +222,13 @@ static void tbs_sched_func(struct gvt_sched_data
> *sched_data)
>  	vgpu = find_busy_vgpu(sched_data);
>  	if (vgpu) {
>  		scheduler->next_vgpu = vgpu;
> -
> -		/* Move the last used vGPU to the tail of lru_list */
>  		vgpu_data = vgpu->sched_data;
> -		list_del_init(&vgpu_data->lru_list);
> -		list_add_tail(&vgpu_data->lru_list,
> -				&sched_data->lru_runq_head);
> +		if (!vgpu_data->pri_sched) {
> +			/* Move the last used vGPU to the tail of lru_list */
> +			list_del_init(&vgpu_data->lru_list);
> +			list_add_tail(&vgpu_data->lru_list,
> +				      &sched_data->lru_runq_head);
> +		}
>  	} else {
>  		scheduler->next_vgpu = gvt->idle_vgpu;
>  	}
> @@ -328,11 +342,17 @@ static void tbs_sched_start_schedule(struct
> intel_vgpu *vgpu)  {
>  	struct gvt_sched_data *sched_data = vgpu->gvt-
> >scheduler.sched_data;
>  	struct vgpu_sched_data *vgpu_data = vgpu->sched_data;
> +	ktime_t now;
> 
>  	if (!list_empty(&vgpu_data->lru_list))
>  		return;
> 
> -	list_add_tail(&vgpu_data->lru_list, &sched_data->lru_runq_head);
> +	now = ktime_get();
> +	vgpu_data->pri_time = ktime_add(now,
> +
> 	ktime_set(GVT_SCHED_VGPU_PRI_TIME, 0));
> +	vgpu_data->pri_sched = true;
> +
> +	list_add(&vgpu_data->lru_list, &sched_data->lru_runq_head);
> 
>  	if (!hrtimer_active(&sched_data->timer))
>  		hrtimer_start(&sched_data->timer,
> ktime_add_ns(ktime_get(),
> --
> 2.18.0