Metal Shader Debugging and Profiling

快来打我* 2022-05-15 15:56 461阅读 0赞

[https://medium.com/@nilotic2/metal-shader-debugging-and-profiling-48da25a400e8][https_medium.com_nilotic2_metal-shader-debugging-and-profiling-48da25a400e8]

# Metal Shader Debugging and Profiling #

## [WWDC 2018][] ##

### Metal Frame Debugger ###

*  Step through API calls
 *  Resource inspection
 *  Shader edit and reload
 *  GPU counters
 *  Pipeline statics
 *  Integrated into Xcode
 *  **Dependency viewer (new)**
 *  **Geometry viewer (new)**
 *  **Shader debugger (new)**
 *  **Enhanced shader profiler (new)**

### Geometry Viewer ###

*  Visualize the post-vertex transform data in 3D
 *  Access to all vertex data
 *  Per-draw call view

### Visibly Wrong Triangles ###

![1_5G3iAj1jQyi6c5-DmOsjNA.gif][]

### Out of Frustum Objects ###

![1_ny7pgt7USL13xsVffbLu7w.gif][]

### Missing Triangles ###

![1_5Nf0pRTqVlrZNnm31Rokag.gif][]

### Why use Shader Debugger? ###

*  Math heavy code
 *  Highly parallel
 *  Unity’s “Book of the Deed”  
    \- ~10 million vertex shader invocations  
    \- ~60 million pixels rendered

![1_HBbfPFyOY2nypC7zQhTQOg.png][]

### Shader Debugging ###

*  New tool for debugging Metal shaders
 *  Rich variable visualization across thousands of threads
 *  Real data from GPU
 *  Flexible stepping
 *  Integrated into Metal Frame Debugger

![1_iT1BPBQ0A6ebWSEKy5JmPQ.png][]

![1_x5SU3-aDWw_xkl-EyRmA-w.png][]

### Demo ###

Problem (negative value)

![1_yjm1bo6MsLMuUcnS-4SJwA.gif][]

--------------------

Fining the bug

![1_Wp0H4Mibwfv2Nty3R_S0GA.gif][]

**Values in realtime**

![1_I0bB_uoufF39T3GA5dv6jQ.gif][]

**Call Stack**

--------------------

Fix the Bug

![1_VsS4ty3V9Ow1WaJCSemAYg.gif][]

--------------------

Refresh

**(You don’t need to rebuild)**

![1_aDxC1T7-540WVbFL7huPVQ.gif][]

--------------------

![1_Gk7EeBrX-dFwRjPE3OxHYQ.gif][]

### Starting the Shader Debugger ###

![1_DjnC7ElBV_FenghTe7Az-A.gif][]

### Inspecting Variables ###

![1_C6ghVJwsFycZGwXBv1qCeQ.png][]

![1_jJL--vsBoNqfLI-fkabw6Q.png][]

![1_TEQI881IpHBcDffU7yfFWQ.png][]

![1_99Y4d2Q3F7tQWvoa_pyb9Q.png][]

### Following the Execution ###

![1_9izHk-xBPkISzt12gt-NfQ.gif][]

Flexible stepping

![1_F9wutKEGROay3Scxu0vP3Q.gif][]

Use filter to focus

### Access to Other Threads ###

Set of threads are available based on the initial selection

*  Vertex — Primitive of the selected vertex
 *  Fragment — Rectangle around the selected pixel
 *  Compute — Threadgroup of the selected thread

### See Variables in Context ###

*  Helps you understand your code
 *  Important to for comparing good/ bad values
 *  Hover for instant access

![1_bdY91J_lgqrhsjw-Wt3xBg.gif][]

### Comparing Good and Bad Pixels ###

*  Quickly compare threads
 *  Execution history and variables and updated for the selected thread

![1_4SduD0pJq2WoXafRHwJJzA.gif][]

### Understanding Divergence ###

*  Mask shows which threads executed the same line to help you understand control flow

![1_jRqUvmlSr20VO3TR1Pirew.png][]

### Demo ###

Problem

![1_SsQA48y1bJVBp0JLcCc7tA.gif][]

--------------------

Finding the Bug

![1_kyyAC56C7Ym94EQokluYFA.gif][]

![1_YKvh4MiZI0kDhCql69EQtw.gif][]

--------------------

![1_J8VXqIu2h3deUk-oZsrcrg.gif][]

### Shader Debugger ###

*  Specifically designed for debugging Metal shaders
 *  Great for  
    \- Fixing bugs!  
    \- Understanding your shader  
    \- Developing your shaders
 *  Supports iOS, macOS, and tvOS
 *  Available in Xcode 10

### Knowing What to Optimized ###

**Profiling tools built into Metal Frame Debugger**

*  GPU counters

![1_PVe-BZW6ED0GKuyb8Z3MCA.png][]

*  Pipeline statistics

![1_nvqBVduIAn0FBpoBO4qS3Q.png][]

*  Shader profiler

![1_59eLicThvpsl1-TUdkts3w.png][]

### Shader Profiler ###

*  Provides per-pipeline timing information

![1_87kBRktjfvAWRa3lLvtisw.png][]

*  Per-line execution cost (iOS and tvOS)

![1_J8ylItx0P0uQu8IxoUmZfA.png][]

*  Shader edit and reload
 *  Get into shader debugger

### Enhanced Shader Profiler for A11 ###

*  Instruction category cost breakdown per line  
    \- ALU — Float, half, and complex  
    \- Memory — Sample, load, and store operations  
    \- Synchronization — Wait memory, barriers, or atomics

![1_NpFm2yqOPE-ia_MF5MaeGA.png][]

*  Visibility into inline function cost

![1_UNZ6u9FncoU2tZlbseUNag.png][]

### Demo ###

![1_P_Rz-0jKdprXblOBLZHe_A.gif][]

### Access to Shader Sources ###

*  New Metal Compiler option
 *  Xcode project  
    \- “Yes, include source code” from build settings
 *  Command line  
    \- “-MO” compiler option

![1_4FefxERw-JH2hkm5b2QDIg.png][]

*  [iOS][]
 *  [Wwdc 2018][]
 *  [Metal][]
 *  [Graphics And Games][]
 *  [Metal Shader][]

[https_medium.com_nilotic2_metal-shader-debugging-and-profiling-48da25a400e8]: https://medium.com/@nilotic2/metal-shader-debugging-and-profiling-48da25a400e8
[WWDC 2018]: https://developer.apple.com/videos/play/wwdc2018/608/
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[iOS]: https://medium.com/tag/ios?source=post
[Wwdc 2018]: https://medium.com/tag/wwdc-2018?source=post
[Metal]: https://medium.com/tag/metal?source=post
[Graphics And Games]: https://medium.com/tag/graphics-and-game?source=post
[Metal Shader]: https://medium.com/tag/metal-shader?source=post