Re: [PATCH] drm/amdgpu: enable bo priority setting from user space

[zhoucm1 <zhoucm1@xxxxxxx>]

On 2019年03月07日 17:55, Michel Dänzer wrote:

On 2019-03-07 10:15 a.m., Chunming Zhou wrote:

Signed-off-by: Chunming Zhou <david1.zhou@xxxxxxx>

Please provide corresponding UMD patches showing how this is to be used.

spec is here:
https://www.khronos.org/registry/vulkan/specs/1.1-extensions/html/vkspec.html, please search "VkMemoryPriorityAllocateInfoEXT".

Fortunately, Windows guy already implemented it before, otherwise, I cannot find ready code on opensource, I hate this chicken first and egg first question :
https://github.com/GPUOpen-Drivers/pal/blob/dev/src/core/gpuMemory.cpp, please search "createInfo.priority".
https://github.com/GPUOpen-Drivers/pal/blob/dev/inc/core/palGpuMemory.h, priority definition is here.

@@ -229,6 +231,14 @@ int amdgpu_gem_create_ioctl(struct drm_device *dev, void *data,
 	if (args->in.domains & ~AMDGPU_GEM_DOMAIN_MASK)
 		return -EINVAL;
 
+	/* check priority */
+	if (args->in.priority == 0) {

Did you verify that this is 0 with old userspace compiled against struct
drm_amdgpu_gem_create_in without the priority field?

Without priority field, I don't think we can check here. Do you mean we need to add a new args struct?

+		/* default is normal */
+		args->in.priority = TTM_BO_PRIORITY_NORMAL;
+	} else if (args->in.priority > TTM_MAX_BO_PRIORITY) {
+		args->in.priority = TTM_MAX_BO_PRIORITY;
+		DRM_ERROR("priority specified from user space is over MAX priority\n");

This must be DRM_DEBUG, or buggy/malicious userspace can spam dmesg.

Will change.

@@ -252,6 +262,7 @@ int amdgpu_gem_create_ioctl(struct drm_device *dev, void *data,
 
 	r = amdgpu_gem_object_create(adev, size, args->in.alignment,
 				     (u32)(0xffffffff & args->in.domains),
+				     args->in.priority - 1,
 				     flags, ttm_bo_type_device, resv, &gobj);

It might be less confusing to subtract 1 after checking against
TTM_MAX_BO_PRIORITY instead of here. Still kind of confusing though. How
about this instead:

Make the priority field of struct drm_amdgpu_gem_create_in signed. In
amdgpu_gem_create_ioctl, clamp the priority to the supported range:

	args->in.priority += TTM_BO_PRIORITY_NORMAL;
	args->in.priority = max(args->in.priority, 0);
	args->in.priority = min(args->in.priority,
				TTM_BO_PRIORITY_NORMAL - 1);

This way userspace doesn't need to do a weird mapping of the priority
values (where 0 and 2 have the same meaning), and the range of supported
priorities could at least theoretically be extended without breaking
userspace.

First, I want to explain a bit the priority value from vulkan:
"    From Vulkan Spec, 0.0 <= value <= 1.0, and the granularity of the priorities is implementation-dependent.
     One thing Spec forced is that if VkMemoryPriority not specified as default behavior, it is as if the
     priority value is 0.5. Our strategy is that map 0.5 to GpuMemPriority::Normal-GpuMemPriorityOffset::Offset0,
     which is consistent to MemoryPriorityDefault. We adopts GpuMemPriority::VeryLow, GpuMemPriority::Low,
     GpuMemPriority::Normal, GpuMemPriority::High, 4 priority grades, each of which contains 8 steps of offests.
     This maps [0.0-1.0) to totally 32 steps. Finally, 1.0 maps to GpuMemPriority::VeryHigh.
"

So my original purpose is directly use Priority enum defined in PAL, like this:
 "
/// Specifies Base Level priority per GPU memory allocation as a hint to the memory manager in the event it needs to
/// select allocations to page out of their preferred heaps.
enum class GpuMemPriority : uint32
{
    Unused    = 0x0,  ///< Indicates that the allocation is not currently being used at all, and should be the first
                      ///  choice to be paged out.
    VeryLow   = 0x1,  ///< Lowest priority to keep in its preferred heap.
    Low       = 0x2,  ///< Low priority to keep in its preferred heap.
    Normal    = 0x3,  ///< Normal priority to keep in its preferred heap.
    High      = 0x4,  ///< High priority to keep in its preferred heap (e.g., render targets).
    VeryHigh  = 0x5,  ///< Highest priority to keep in its preferred heap.  Last choice to be paged out (e.g., page
                      ///  tables, displayable allocations).
    Count
};
"

If according your idea, we will need to convert it again when hooking linux implementation.
So what do think we still use unsigned?

@@ -304,6 +315,7 @@ int amdgpu_gem_userptr_ioctl(struct drm_device *dev, void *data,
 
 	/* create a gem object to contain this object in */
 	r = amdgpu_gem_object_create(adev, args->size, 0, AMDGPU_GEM_DOMAIN_CPU,
+				     TTM_BO_PRIORITY_NORMAL,
 				     0, ttm_bo_type_device, NULL, &gobj);

Should the userptr ioctl also allow setting the priority?

We can.

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
index fd9c4beeaaa4..c85304e03021 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
@@ -494,8 +494,9 @@ static int amdgpu_bo_do_create(struct amdgpu_device *adev,
 
 	bo->tbo.bdev = &adev->mman.bdev;
 	amdgpu_bo_placement_from_domain(bo, bp->domain);
+	bo->tbo.priority = bp->priority;
 	if (bp->type == ttm_bo_type_kernel)
-		bo->tbo.priority = 1;
+		bo->tbo.priority = TTM_BO_PRIORITY_VERYHIGH;

	if (bp->type == ttm_bo_type_kernel)
		bo->tbo.priority = TTM_BO_PRIORITY_VERYHIGH;
	else
		bo->tbo.priority = bp->priority;

would be clearer I think.

Agree.

-David

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