Porting Source 2 to Vulkan - PowerPoint Presentation

360 views
Uploaded On 2018-02-20

Porting Source 2 to Vulkan - PPT Presentation

Dan Ginsburg Valve Summary Source 2 Overview Porting to Vulkan Shaders and Pipelines Command Buffers Memory Management Descriptor Sets Source 2 Overview Source 2 OpenGL DX9 DX11 Vulkan ID: 633504

command thread buffers source thread command source buffers descriptor sets cmdbuf dynamic dx11 pools offset perf buffer memory queue

Link:

Copy

Embed:

<iframe width="560" height="315" src="https://www.docslides.com/embed/633504" frameborder="0" allowfullscreen></iframe>

Download Presentation from below link

Download Presentation The PPT/PDF document "Porting Source 2 to Vulkan" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.

Presentation Transcript

Slide1
Slide2

Porting Source 2 to

VulkanDan GinsburgValveSlide3

Summary

Source 2 OverviewPorting to VulkanShaders and PipelinesCommand BuffersMemory Management

Descriptor SetsSlide4

Source 2 OverviewSlide5

Source 2

OpenGL, DX9, DX11, VulkanWindows, Linux, MacDota 2 RebornSlide6

Source 2 Rendering

DX11-like rendersystem abstractionMultithreadedDX9/GL: software command buffers DX11: deferred contextsSingle submission threadSlide7

Source 2 Rendering (GL)Slide8

Source 2 Vulkan Port

Started with GL and DX11 rendererDX11 deferred contexts mapped well to Vulkan command buffersLeveraged GLSL shader conversionSlide9

Shaders and PipelinesSlide10

Porting Shaders to Vulkan

HLSL -> GLSLSee: Moving Your Games to OpenGL, Steam Dev Days 2014GLSL -> SPIR-VDescriptor set layout qualifiers to GLSLOpen source

glslang SPIR-V backendSPVremapper for compression

https://github.com/KhronosGroup/glslangSlide11

Pipeline State Objects (PSOs)

Each thread caches pipeline stateGlobal pipeline managerPSO MapPending and currentReduces mutexing

End of Frame

Pending PSO Map

Current PSO Map

PSO0

PSO1

PSO2

Pipeline State Hash

Create PSO

Lookup

PSO3

LookupSlide12

Command BuffersSlide13

Command Buffers

Used where DX11 deferred contexts were usedEach thread builds command bufferSingle thread performs submission to queueSlide14

Command Buffers

Recycled within per-thread poolsThread 0 CommandPool

Thread 1 CommandPool

CmdBuf

Submit1

Submit2

Thread 2

CommandPool

Thread0

Thread1

Thread2

Submit

Main

Check FencesSlide15

Command Buffer Performance

Submit in batchesvkQueueSubmit has cost on WindowsFaster to group submissions togetherMinimize number of command buffersMinimize memory referenced per command bufferUse VK_CMD_BUFFER_OPTIMIZE_ONE_TIME_SUBMIT_BITOptimize for one-time submission Slide16

Memory ManagementSlide17

General Strategies

Pool resources togetherReduces memory reference countUse per-thread pools to reduce contentionRecycle dynamic pools on frame boundariesSlide18

Resources

Static ResourcesDynamic ResourcesGlobal PoolsDevice Only

Textures/Render Targets128MB Pools

VB/IB/CBs8MB PoolsPer-Thread Pools

Host Visible (Persistently Mapped)

VB/IB/CBs

8MB PoolsSlide19

Dynamic Vertex/Index Buffers

To update:Grab new offset from per-thread poolmemcpy into poolBind VBs with: vkCmdBindVertexBuffers(..,buffer,offset)Bind IBs with:

vkCmdBindIndexBuffer(..,buffer,offset,..)Recycle pools when last GPU fence of frame retiresSlide20

Dynamic

Uniform BuffersDifferences from VB/IBs:UBOs are bound via descriptorsUse dynamic UBOs to avoid vkUpdateDescriptors

Pass UBO offset to vkCmdBindDescriptorSetsSlide21

Dynamic Textures

Staged in persistently mapped buffersRecycled per-frameCopy with vkCmdCopyBufferToImageSlide22

Descriptor SetsSlide23

Descriptor Set - Ideal

Allocate and bake descriptor sets up frontGroup sets by update frequencyOnly update changed setsSlide24

Descriptor Set - Reality

Difficult to bake descriptors with DX11-like abstractionOur approachPre-allocate descriptor sets with fixed slotsOnly bind to used slotsUpdate descriptors each drawSlide25

Allocating Descriptor Sets

Allocated from per-thread poolsPre-allocate on pool creation and recycle on frame boundariesGrab new descriptor set by just incrementing offsetSlide26

Future optimizations

Group resources into multiple setsUse dynamic UBOs to avoid updating UBO descriptorsBake texture bindings higher up in abstractionAvoid updating descriptors where possibleSlide27

MiscellaneousSlide28

Swap Queue Depth

Manage yourselfWindow System Interaction (WSI) extensionCreate N images for swap queue depthFence or semaphore to manage swap queue depthSlide29

Image Layout Transitions

Transitions require previous and new layoutExample: Color Attachment -> Shader ReadCommand buffers generated out-of-orderProblem: how do we know previous layout?OptionsReturn image layouts to known statesGood for CPU Perf, Bad for GPU PerfGenerate command buffers to transition layouts

Bad for CPU Perf, Good for GPU Perf

Tried both:Better for CPU perfBetter for GPU perfSlide30

Coordinate Systems

D3D11 conventions, except:Y direction of clipspace is invertedIf porting from HLSL:Invert gl_Position.yReasoning: kept all spaces consistentSlide31

Summary

Source 2 OverviewPorting to VulkanShaders and PipelinesCommand Buffers

Memory ManagementDescriptor SetsSlide32

Questions?

dang@valvesoftware.comKhronos BOF:Wed. August 12th, 5:30-7:30JW Marriott LA Live in the Platinum Ballroom Salon F-I