[PATCH 2/2] drm/i915/gvt: Audit and shadow workload during ELSP writing

[Gao, Ping A]

On 2017/6/5 16:38, Wang, Zhi A wrote:
>
> On 05/24/17 20:49, Ping Gao wrote:
>> Let the workload audit and shadow ahead of vGPU scheduling, that
>> will eliminate GPU idle time and improve performance for multi-VM.
>>
>> The performance of Heaven running simultaneously in 3VMs has
>> improved 20% after this patch.
>>
>> Signed-off-by: Ping Gao <ping.a.gao at intel.com>
>> ---
>>   drivers/gpu/drm/i915/gvt/execlist.c  | 12 ++++++++++++
>>   drivers/gpu/drm/i915/gvt/scheduler.c |  7 +++++++
>>   drivers/gpu/drm/i915/gvt/scheduler.h |  1 +
>>   3 files changed, 20 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/gvt/execlist.c b/drivers/gpu/drm/i915/gvt/execlist.c
>> index dca989e..a14cf29 100644
>> --- a/drivers/gpu/drm/i915/gvt/execlist.c
>> +++ b/drivers/gpu/drm/i915/gvt/execlist.c
>> @@ -605,6 +605,7 @@ static int submit_context(struct intel_vgpu *vgpu, int ring_id,
>>   	struct list_head *q = workload_q_head(vgpu, ring_id);
>>   	struct intel_vgpu_workload *last_workload = get_last_workload(q);
>>   	struct intel_vgpu_workload *workload = NULL;
>> +	struct drm_i915_private *dev_priv = vgpu->gvt->dev_priv;
>>   	u64 ring_context_gpa;
>>   	u32 head, tail, start, ctl, ctx_ctl, per_ctx, indirect_ctx;
>>   	int ret;
>> @@ -668,6 +669,7 @@ static int submit_context(struct intel_vgpu *vgpu, int ring_id,
>>   	workload->complete = complete_execlist_workload;
>>   	workload->status = -EINPROGRESS;
>>   	workload->emulate_schedule_in = emulate_schedule_in;
>> +	workload->shadowed = false;
>>
>>   	if (ring_id == RCS) {
>>   		intel_gvt_hypervisor_read_gpa(vgpu, ring_context_gpa +
>> @@ -701,6 +703,16 @@ static int submit_context(struct intel_vgpu *vgpu, int ring_id,
>>   		return ret;
>>   	}
>>
>> +	/* Only audit and shadow the first workload in the queue
>> +	 * as there is only one pre-allocated buf-obj for shadow.
>> +	 */
>> +	if (vgpu->gvt->scheduler.current_vgpu != vgpu &&
>> +				list_empty(workload_q_head(vgpu, ring_id))) {
>> +		mutex_lock(&dev_priv->drm.struct_mutex);
>> +		intel_gvt_audit_and_shadow_workload(workload);
>> +		mutex_unlock(&dev_priv->drm.struct_mutex);
>> +	}
>> +
> Is there any reason why a pre-shadow cannot happen when current_vgpu == 
> vgpu and workload q is empty?

As there is only one pre-allocated obj-buf for shadow, it's able to
shadow the first workload only in the q. The q is empty before inqueue
means current workload will be the first node of the q.

current_vgpu!=vgpu, it try to emphasize that the performance could get
improved only when pre-shadow happen under this condition , that's why
we need pre-shadow. Logically it can be removed but the purpose of
pre-shadow would be not very clear when reading the code.

>>   	queue_workload(workload);
>>   	return 0;
>>   }
>> diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c b/drivers/gpu/drm/i915/gvt/scheduler.c
>> index d6bfdfe..4261bd1 100644
>> --- a/drivers/gpu/drm/i915/gvt/scheduler.c
>> +++ b/drivers/gpu/drm/i915/gvt/scheduler.c
>> @@ -184,6 +184,11 @@ int intel_gvt_audit_and_shadow_workload(struct intel_vgpu_workload *workload)
>>   	struct intel_ring *ring;
>>   	int ret;
>>
>> +	if (workload->shadowed) {
>> +		ret = workload->status;
>> +		return ret;
>> +	}
>> +
>>   	shadow_ctx->desc_template &= ~(0x3 << GEN8_CTX_ADDRESSING_MODE_SHIFT);
>>   	shadow_ctx->desc_template |= workload->ctx_desc.addressing_mode <<
>>   				    GEN8_CTX_ADDRESSING_MODE_SHIFT;
>> @@ -230,6 +235,8 @@ int intel_gvt_audit_and_shadow_workload(struct intel_vgpu_workload *workload)
>>   	if (ret)
>>   		goto out;
>>
>> +	workload->shadowed = true;
>> +
>>   out:
>>   	workload->status = ret;
>>   	return ret;
>> diff --git a/drivers/gpu/drm/i915/gvt/scheduler.h b/drivers/gpu/drm/i915/gvt/scheduler.h
>> index 2cd725c..575659e 100644
>> --- a/drivers/gpu/drm/i915/gvt/scheduler.h
>> +++ b/drivers/gpu/drm/i915/gvt/scheduler.h
>> @@ -78,6 +78,7 @@ struct intel_vgpu_workload {
>>   	struct drm_i915_gem_request *req;
>>   	/* if this workload has been dispatched to i915? */
>>   	bool dispatched;
>> +	bool shadowed;
>>   	int status;
>>
>>   	struct intel_vgpu_mm *shadow_mm;
>>