Re: [PATCH v4 7/7] drm/i915/gvt: rw more pages a time for shadow context

[Zhenyu Wang <zhenyuw@linux.intel.com>]

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On 2020.03.12 23:12:33 -0400, Yan Zhao wrote:
> 1. as shadow context is pinned in intel_vgpu_setup_submission() and
> unpinned in intel_vgpu_clean_submission(), its base virtual address of
> is safely obtained from lrc_reg_state. no need to call kmap()/kunmap()
> repeatedly.
> 
> 2. IOVA(GPA)s of context pages are checked in this patch and if they are
> consecutive, read/write them together in one
> intel_gvt_hypervisor_read_gpa() / intel_gvt_hypervisor_write_gpa().
> 
> after the two changes in this patch,

Better split the kmap remove and consecutive copy one for bisect.

> average cycles for populate_shadow_context() and update_guest_context()
> are reduced by ~10000-20000 cycles, depending on the average number of
> consecutive pages in each read/write.
> 
> (1) comparison of cycles of
> populate_shadow_context() + update_guest_context() when executing
> different benchmarks
>  -------------------------------------------------------------
> |       cycles      | glmark2     | lightsmark  | openarena   |
> |-------------------------------------------------------------|
> | before this patch | 65968       | 97852       | 61373       |
> |  after this patch | 56017 (85%) | 73862 (75%) | 47463 (77%) |
>  -------------------------------------------------------------
> 
> (2) average count of pages read/written a time in
> populate_shadow_context() and update_guest_context()
> for each benchmark
> 
>  -----------------------------------------------------------
> |     page cnt      | glmark2     | lightsmark  | openarena |
> |-----------------------------------------------------------|
> | before this patch |    1        |      1      |    1      |
> |  after this patch |    5.25     |     19.99   |   20      |
>  ------------------------------------------------------------
> 
> (3) comparison of benchmarks scores
>  ---------------------------------------------------------------------
> |      score        | glmark2       | lightsmark     | openarena      |
> |---------------------------------------------------------------------|
> | before this patch | 1244          | 222.18         | 114.4          |
> |  after this patch | 1248 (100.3%) | 225.8 (101.6%) | 115.0 (100.9%) |
>  ---------------------------------------------------------------------
> 
> Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
> ---
>  drivers/gpu/drm/i915/gvt/scheduler.c | 95 ++++++++++++++++++++--------
>  1 file changed, 67 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c b/drivers/gpu/drm/i915/gvt/scheduler.c
> index 1c95bf8cbed0..852d924f6abc 100644
> --- a/drivers/gpu/drm/i915/gvt/scheduler.c
> +++ b/drivers/gpu/drm/i915/gvt/scheduler.c
> @@ -128,16 +128,21 @@ static int populate_shadow_context(struct intel_vgpu_workload *workload)
>  {
>  	struct intel_vgpu *vgpu = workload->vgpu;
>  	struct intel_gvt *gvt = vgpu->gvt;
> -	struct drm_i915_gem_object *ctx_obj =
> -		workload->req->context->state->obj;
> +	struct intel_context *ctx = workload->req->context;
>  	struct execlist_ring_context *shadow_ring_context;
> -	struct page *page;
>  	void *dst;
> +	void *context_base;
>  	unsigned long context_gpa, context_page_num;
> +	unsigned long gpa_base; /* first gpa of consecutive GPAs */
> +	unsigned long gpa_size; /* size of consecutive GPAs */
>  	int i;
>  
> -	page = i915_gem_object_get_page(ctx_obj, LRC_STATE_PN);
> -	shadow_ring_context = kmap(page);
> +	GEM_BUG_ON(!intel_context_is_pinned(ctx));
> +
> +	context_base = (void *) ctx->lrc_reg_state -
> +				(LRC_STATE_PN << I915_GTT_PAGE_SHIFT);
> +
> +	shadow_ring_context = (void *) ctx->lrc_reg_state;
>  
>  	sr_oa_regs(workload, (u32 *)shadow_ring_context, true);
>  #define COPY_REG(name) \
> @@ -169,7 +174,6 @@ static int populate_shadow_context(struct intel_vgpu_workload *workload)
>  			I915_GTT_PAGE_SIZE - sizeof(*shadow_ring_context));
>  
>  	sr_oa_regs(workload, (u32 *)shadow_ring_context, false);
> -	kunmap(page);
>  
>  	if (IS_RESTORE_INHIBIT(shadow_ring_context->ctx_ctrl.val))
>  		return 0;
> @@ -184,8 +188,12 @@ static int populate_shadow_context(struct intel_vgpu_workload *workload)
>  	if (IS_BROADWELL(gvt->gt->i915) && workload->engine->id == RCS0)
>  		context_page_num = 19;
>  
> -	i = 2;
> -	while (i < context_page_num) {
> +
> +	/* find consecutive GPAs from gma until the first inconsecutive GPA.
> +	 * read from the continuous GPAs into dst virtual address
> +	 */
> +	gpa_size = 0;
> +	for (i = 2; i < context_page_num; i++) {
>  		context_gpa = intel_vgpu_gma_to_gpa(vgpu->gtt.ggtt_mm,
>  				(u32)((workload->ctx_desc.lrca + i) <<
>  				I915_GTT_PAGE_SHIFT));
> @@ -194,12 +202,24 @@ static int populate_shadow_context(struct intel_vgpu_workload *workload)
>  			return -EFAULT;
>  		}
>  
> -		page = i915_gem_object_get_page(ctx_obj, i);
> -		dst = kmap(page);
> -		intel_gvt_hypervisor_read_gpa(vgpu, context_gpa, dst,
> -				I915_GTT_PAGE_SIZE);
> -		kunmap(page);
> -		i++;
> +		if (gpa_size == 0) {
> +			gpa_base = context_gpa;
> +			dst = context_base + (i << I915_GTT_PAGE_SHIFT);
> +		} else if (context_gpa != gpa_base + gpa_size)
> +			goto read;
> +
> +		gpa_size += I915_GTT_PAGE_SIZE;
> +
> +		if (i == context_page_num - 1)
> +			goto read;
> +
> +		continue;
> +
> +read:
> +		intel_gvt_hypervisor_read_gpa(vgpu, gpa_base, dst, gpa_size);
> +		gpa_base = context_gpa;
> +		gpa_size = I915_GTT_PAGE_SIZE;
> +		dst = context_base + (i << I915_GTT_PAGE_SHIFT);
>  	}
>  	return 0;
>  }
> @@ -784,19 +804,23 @@ static void update_guest_context(struct intel_vgpu_workload *workload)
>  {
>  	struct i915_request *rq = workload->req;
>  	struct intel_vgpu *vgpu = workload->vgpu;
> -	struct drm_i915_gem_object *ctx_obj = rq->context->state->obj;
> +	struct intel_context *ctx = workload->req->context;
>  	struct execlist_ring_context *shadow_ring_context;
> -	struct page *page;
> -	void *src;
>  	unsigned long context_gpa, context_page_num;
> +	unsigned long gpa_base; /* first gpa of consecutive GPAs */
> +	unsigned long gpa_size; /* size of consecutive GPAs*/
>  	int i;
>  	u32 ring_base;
>  	u32 head, tail;
>  	u16 wrap_count;
> +	void *src;
> +	void *context_base;
>  
>  	gvt_dbg_sched("ring id %d workload lrca %x\n", rq->engine->id,
>  		      workload->ctx_desc.lrca);
>  
> +	GEM_BUG_ON(!intel_context_is_pinned(ctx));
> +
>  	head = workload->rb_head;
>  	tail = workload->rb_tail;
>  	wrap_count = workload->guest_rb_head >> RB_HEAD_WRAP_CNT_OFF;
> @@ -820,9 +844,14 @@ static void update_guest_context(struct intel_vgpu_workload *workload)
>  	if (IS_BROADWELL(rq->i915) && rq->engine->id == RCS0)
>  		context_page_num = 19;
>  
> -	i = 2;
> +	context_base = (void *) ctx->lrc_reg_state -
> +			(LRC_STATE_PN << I915_GTT_PAGE_SHIFT);
>  
> -	while (i < context_page_num) {
> +	/* find consecutive GPAs from gma until the first inconsecutive GPA.
> +	 * write to the consecutive GPAs from src virtual address
> +	 */
> +	gpa_size = 0;
> +	for (i = 2; i < context_page_num; i++) {
>  		context_gpa = intel_vgpu_gma_to_gpa(vgpu->gtt.ggtt_mm,
>  				(u32)((workload->ctx_desc.lrca + i) <<
>  					I915_GTT_PAGE_SHIFT));
> @@ -831,19 +860,30 @@ static void update_guest_context(struct intel_vgpu_workload *workload)
>  			return;
>  		}
>  
> -		page = i915_gem_object_get_page(ctx_obj, i);
> -		src = kmap(page);
> -		intel_gvt_hypervisor_write_gpa(vgpu, context_gpa, src,
> -				I915_GTT_PAGE_SIZE);
> -		kunmap(page);
> -		i++;
> +		if (gpa_size == 0) {
> +			gpa_base = context_gpa;
> +			src = context_base + (i << I915_GTT_PAGE_SHIFT);
> +		} else if (context_gpa != gpa_base + gpa_size)
> +			goto write;
> +
> +		gpa_size += I915_GTT_PAGE_SIZE;
> +
> +		if (i == context_page_num - 1)
> +			goto write;
> +
> +		continue;
> +
> +write:
> +		intel_gvt_hypervisor_write_gpa(vgpu, gpa_base, src, gpa_size);
> +		gpa_base = context_gpa;
> +		gpa_size = I915_GTT_PAGE_SIZE;
> +		src = context_base + (i << I915_GTT_PAGE_SHIFT);
>  	}
>  
>  	intel_gvt_hypervisor_write_gpa(vgpu, workload->ring_context_gpa +
>  		RING_CTX_OFF(ring_header.val), &workload->rb_tail, 4);
>  
> -	page = i915_gem_object_get_page(ctx_obj, LRC_STATE_PN);
> -	shadow_ring_context = kmap(page);
> +	shadow_ring_context = (void *) ctx->lrc_reg_state;
>  
>  #define COPY_REG(name) \
>  	intel_gvt_hypervisor_write_gpa(vgpu, workload->ring_context_gpa + \
> @@ -861,7 +901,6 @@ static void update_guest_context(struct intel_vgpu_workload *workload)
>  			sizeof(*shadow_ring_context),
>  			I915_GTT_PAGE_SIZE - sizeof(*shadow_ring_context));
>  
> -	kunmap(page);
>  }
>  
>  void intel_vgpu_clean_workloads(struct intel_vgpu *vgpu,
> -- 
> 2.17.1
> 

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