[PATCH v2] drm/i915/gvt: avoid unnecessary vgpu switch

[Ping Gao]

It's no need to switch vgpu if next vgpu is the same with current
vgpu, otherwise it will make performance drop in some case.

v2: correct the comments.

Signed-off-by: Ping Gao <ping.a.gao at intel.com>
---
 drivers/gpu/drm/i915/gvt/sched_policy.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/sched_policy.c b/drivers/gpu/drm/i915/gvt/sched_policy.c
index 79ba4b3..f25ff13 100644
--- a/drivers/gpu/drm/i915/gvt/sched_policy.c
+++ b/drivers/gpu/drm/i915/gvt/sched_policy.c
@@ -129,9 +129,13 @@ static void try_to_schedule_next_vgpu(struct intel_gvt *gvt)
 	struct vgpu_sched_data *vgpu_data;
 	ktime_t cur_time;
 
-	/* no target to schedule */
-	if (!scheduler->next_vgpu)
+	/* no need to schedule if next_vgpu is the same with current_vgpu,
+	 * let scheduler chose next_vgpu again by setting it to NULL.
+	 */
+	if (scheduler->next_vgpu == scheduler->current_vgpu) {
+		scheduler->next_vgpu = NULL;
 		return;
+	}
 
 	/*
 	 * after the flag is set, workload dispatch thread will
-- 
1.9.1