Chromium

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Chromium

• Mike Houston, Stanford University
• and
• The Chromium Community

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How Chromium works

• Replaces systems OpenGL driver
• Industry standard API
• Support existing unmodified applications
• Manipulates streams of API commands
• Alter/inject/discard commands and parameters
• Route commands over a network
• Render commands using graphics hardware
• State tracking
• Allows parallel applications to issue OpenGL
• Constrain ordering between multiple streams

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Graphics Stream Processing

• Treat OpenGL calls as a stream of commands
• Form a DAG of stream transformation nodes
• Nodes are computers in a cluster
• Edges are OpenGL API communication
• Each node has a serialization stage and a
  transformation stage

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Stream Serialization

• Convert multiple streams into a single stream
• Efficiently context-switch between streams
• Constrain ordering using Parallel OpenGL
  extensions Igehy98
• Two kinds of serializers
• Network server
• Application
• Unmodified serial application
• Custom parallel application

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Stream Transformation

• Serialized stream is dispatched to Stream
  Processing Units (SPUs)
• Each SPU is a shared library
• Exports a (partial) OpenGL interface
• Each node loads a chain of SPUs at run time
• SPUs are generic and interchangeable

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SPU Chains

• SPUs are loaded as parts of linear chains
• Common usage intercept a few OpenGL calls, pass
  all others to downstream SPU
• Useful for simple state changes, such as
  wireframe drawing

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Output Scalability (Sort-First)
App

• Larger displays with unmodified applications
• Other possibilities broadcast, ring network

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Example Sort-First
App
Tilesort
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Input Scalability (Sort-Last)
Server

• Parallel geometry extraction
• Parallel data submission

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Example Sort-Last
Server
Render

• Application runs directly on graphics hardware
• Same application can use sort-last or sort-first

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SPU Inheritance

• The Readback and Render SPUs are related
• Readback renders everything except SwapBuffers
• Readback inherits from the Render SPU
• Override parents implementation of SwapBuffers
• All OpenGL calls considered virtual

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Readbacks SwapBuffers
void RB_SwapBuffers(void) self.ReadPixels(
0, 0, w, h, ... ) child.Clear(
GL_COLOR_BUFFER_BIT ) child.SemaphorePCR(
READBACK_SEMAPHORE ) child.RasterPos2i( tileX,
tileY ) child.DrawPixels( w, h, ... )
child.SemaphoreVCR( READBACK_SEMAPHORE )
child.SwapBuffers( )

• Easily extended to include depth composite
• All other functions inherited from Render SPU

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More Complicated Example Hybrid
Server
Render
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Networks Supported

• TCP/UDP
• Myrinet
• Quadrics
• Infiniband (coming soon)

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New Things to Chromium

• Extensions
• DMX Support
• Display list management (DLM)
• VNC Support
• CRUT

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Extensions

• GL_ARB_fragment_program
• GL_ARB_vertex_program
• GL_NV_fragment_program
• GL_NV_vertex_program
• GL_NV_texture_rectangle
• GL_EXT_shadow_funcs
• GL_EXT_texture_rectangle
• GL_IBM_raster_pos_clip

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DMX Support

• DMX
• Distributed Multi-headed X
• Single X session across multiple-displays
• OpenGL through Chromium
• Chromium DMX aware
• Moving/resizing retiling
• M to N rendering

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DMX In Action
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Display List Management

• Display List Manager (DLM)
• State tracking is really tricky
• Replay state calls on client
• Call list on servers
• Bounding Box tracking of display list
• Future optimizations
• Avoid broadcasting data in display list
• Send calls once per server as needed

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VNC

• X forwarding
• Forwards GLX calls to client
• DRI bypasses X
• Cant get pixel data
• OpenGL apps load Chromium
• Render on local host
• Readback pixel data
• Send to users display

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What are people doing with Chromium?
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Dynamic Screen Calibration
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Quake3 Arena
Niederauer, et al.
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Viewed in a new way
Niederauer, et al.
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Architectural Analysis

• Intercept geometry
• Determine floor positions
• Change to orthographic view
• Insert clip planes at the ceilings
• Split floors apart
• Multi-pass rendering

Non-Invasive Interactive Visualization of
Dynamic Architectural Environments Christopher
Niederauer, Mike Houston, Maneesh Agrawala, Greg
HumphreysACM SIGGRAPH 2003 Symposium on
Interactive 3D Graphics
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Batch Scheduler Integration

• Offline rendering to a webpage
• Use massive compute resources
• Rendering with Vis cluster
• Integrate support with RMS

Pittsburg Supercomputer Center
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Terascale Computing System
Summary

• 750 Compute Nodes
• 3000 EV68 processors
• 6 Tf (peak, est gt4Tf on LSMS)
• 3. TB memory
• 27 TB local disk
• Multi-rail fat-tree network
• Redundant monitor/ctrl
• WAN/LAN accessible
• Parallel visualization
• File servers 30TB, 32 GB/s
• Mass store, 1 TB/hr

WAN/LAN
Pittsburg Supercomputer Center
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Example

• qsub l rmsnodes312,othervisnodes5
• Job waits until 3 nodes (12 cpus) become
  available AND 5 vis nodes are available
• When resources available, job runs
• Visit vis web page for rendering

Pittsburg Supercomputer Center
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What coming in the next year?
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General Improvements

• Continue to track OpenGL changes
• Add extensions
• Optimizations
• Display list management
• Tilesort
• Software Compositors

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PICA Support

• Parallel Image Compositing API (PICA)
• API for hardware and software compositing
• Will be supported by most hardware compositors
• Chromium support
• Hooks almost complete
• Need software compositors
• Readback (N to 1)
• Binary-swap
• SLIC
• Need info from hardware folks

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Vis as a service

• Better integration with schedulers
• Reservation systems
• Compute/Render/Display
• Distributed event model (CRUT)
• Compression
• Geometry data
• Pixel data
• Encryption

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Look at how much was done last year!

• 4 releases
• Constant bug fixes
• Constant improvements
• Constant optimizations

Chromium is supported by a large community!
Chromium is used in the real world!
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Go get it!
http//chromium.sourceforge.net
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Acknowlegements

• The Chromium community
• Greg Humphreys
• Brian Paul
• Joel Welling
• Alan Hourihane
• DOE!!!