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GPU Filesystem for Plan 9
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Joel Fridolin Meyer
.CW \s-3joel@sirjofri.de\s0
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10th International Workshop on Plan 9
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\s-3April 12-14 2024\s0
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What is a GPU?
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.PS <what.p
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Coprocessor
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``Separate Computer''
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``Graphics'' Processing Unit
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Single Instruction, Multiple Data (SIMD)
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Application Architecture
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.PS <arch.p
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Resource Abstraction (Plug and Play)
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9P Performance?
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Scalability on the application level
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Inspired by Vulkan
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Designed by Khronos
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Lowlevel API
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Abstract and cross-platform
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Shaders and buffers as objects
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Inspired by Vulkan
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Designed by Khronos
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Lowlevel API
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Abstract and cross-platform
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Shaders and buffers as objects
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.PS <comp.p
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Shader Compilation
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.PS <glsl.p
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.IP •
Lots of magic happens in the driver
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SPIR-V program is cross-platform
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Filesystem Interface
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Filesystem Interface
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.IP •
Simple to understand
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Generic enough to be portable
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Plug and Play
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GPGPU first (compute shader)
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Filesystem Interface
.sp .5i
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.ft CW
/dev/gpu
/ctl \fR\f(CW
/desc \fRdescriptor table\f(CW
/0/ctl \fRobject 0 ctl file\f(CW
/0/buffer \fRbuffer data\f(CW
/1/ctl \fRobject 1 ctl file\f(CW
/1/shader \fRshader program\f(CW
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Filesystem Interface
.sp .5i
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.ft CW
/dev/gpu
/ctl \fR\f(CW
/desc \fRdescriptor table\f(CW
/0/ctl \fRobject 0 ctl file\f(CW
/0/buffer \fRbuffer data\f(CW
/1/ctl \fRobject 1 ctl file\f(CW
/1/shader \fRshader program\f(CW
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; echo n b 4 > ctl # object 0, buffer 4 bytes
; echo n s > ctl # object 1, shader
; cp buffer.bin 0/buffer
; cp shader.spv 1/shader
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Filesystem Interface
.sp .5i
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DescPool 0
Set 0
0 -1 \fR(unbound)\f(CW
1 0 \fR(Buffer 0)\f(CW
2 -1 \fR(unbound)\f(CW
3 -1 \fR(unbound)\f(CW
Set 1
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.sp .5i
.IP •
Shader is bound to a descriptor pool
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Buffer is bound to a specific binding
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Shader program knows which set+binding to access
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Example Shader Program
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#version 450 core
layout(std430, set = 0, binding = 1) buffer pos
{
vec4 positions[];
};
layout(local_size_x = 1000,
local_size_y = 1, local_size_z = 1) in;
void main() {
vec4 position =
positions[gl_GlobalInvocationID.x];
// do something beautiful
}
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Workgroups
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Number of workgroups (set by application)
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Workgroup size (compiled in the shader; \f(CWlocal_size_x\fR, …)
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Both are 3D vectors
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#(Invocations) = #(workgroups) · (Workgroup size)
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Implementation
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Draft Implementation (CPU)
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Drawterm (GPU, Vulkan SDK)
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Possible others? (SSE/CPU, network, hardware, …)
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\s+5\fBThank you\fR\s0
Questions?
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