Quartz 5

虚拟地址VMM

4 min read

基本使用

  • 掌握虚拟地址的基本使用
  • 验证虚拟地址可以重复使用

基本思路

  • 应用虚拟地址创建数据，并运算矩阵乘法；
  • 一共有两个矩阵乘法，依次运算；
  • 第一个矩阵乘法运算完后释放物理显存，但不释放虚拟地址继续用于第二个矩阵乘法。
  • 第二个矩阵运算完后，比较两次的地址与结果。
root@node201:/workspace/infrawaves/zhangmj/BasicCUDA/memory_opt/vmm# ./reuse_virtual_address
=== Dynamic Virtual Memory Matrix Multiplication Demo ===
Matrix size: 256x256
Elements per matrix: 65536
Original matrix size: 262144 bytes
 
--- Phase 1: Using first dataset ---
GPU Compute Capability: 9.0
Virtual Memory Management Supported: YES
Creating context using cuDevicePrimaryCtxRetain...
Successfully reserved virtual address: 0x7f9485e00000 (size: 2097152 bytes)
GPU Compute Capability: 9.0
Virtual Memory Management Supported: YES
Creating context using cuDevicePrimaryCtxRetain...
Successfully reserved virtual address: 0x7f948a800000 (size: 2097152 bytes)
GPU Compute Capability: 9.0
Virtual Memory Management Supported: YES
Creating context using cuDevicePrimaryCtxRetain...
Successfully reserved virtual address: 0x7f948aa00000 (size: 2097152 bytes)
Physical memory mapped to virtual address 0x7f9485e00000
Physical memory mapped to virtual address 0x7f948a800000
Physical memory mapped to virtual address 0x7f948aa00000
Virtual addresses: A=0x7f9485e00000, B=0x7f948a800000, C=0x7f948aa00000
Executing matrix multiplication (first dataset)...
Phase 1 computation complete
Phase 1 result sum (first 5 elements): 20940
 
--- Phase 2: Dynamic switch to second dataset ---
Unmapped virtual address
Unmapped virtual address
Physical memory mapped to virtual address 0x7f9485e00000
Physical memory mapped to virtual address 0x7f948a800000
Virtual addresses comparison:
A: 0x7f9485e00000 -> 0x7f9485e00000 (same: YES)
B: 0x7f948a800000 -> 0x7f948a800000 (same: YES)
Virtual address consistency verified!
Executing matrix multiplication (second dataset)...
Phase 2 computation complete
 
--- Result Verification ---
Phase 1 result sum (first 5 elements): 20940
Phase 2 result sum (first 5 elements): 182698
Results are different - new data was successfully used!
Unmapped virtual address
Freed virtual address space
Unmapped virtual address
Freed virtual address space
Unmapped virtual address
Freed virtual address space
 
 --- Demo completed successfully! ---

虚拟地址与cuda Graph

本例目的：

  • 演示虚拟地址与CUDA Graph配合使用；
  • 虚拟地址保持不变，不会触发CUDA Graph的重新编译。

测试中验证Graph是否需要重编译，函数：cudaGraphExecUpdate

virtual_mem_with_cuda_graph.cu

代码：virtual_mem_with_cuda_graph.cu

编译方式：nvcc -o virtual_mem_with_cuda_graph virtual_mem_with_cuda_graph.cu -lcuda

运行方式： ./virtual_mem_with_cuda_graph

root@node201:/workspace/infrawaves/zhangmj/BasicCUDA/memory_opt/vmm# ./virtual_mem_with_cuda_graph 
=== CUDA Graph with Virtual Memory and Update Check ===
Matrix size: 256x256
Matrix size: 0 MB
 
--- Phase 1: Initial Graph Capture ---
Reserved VA: 0x7f32ade00000 (aligned: 2097152 bytes)
Reserved VA: 0x7f32b2800000 (aligned: 2097152 bytes)
Reserved VA: 0x7f32b2a00000 (aligned: 2097152 bytes)
Mapped physical memory to VA: 0x7f32ade00000
Mapped physical memory to VA: 0x7f32b2800000
Mapped physical memory to VA: 0x7f32b2a00000
Virtual addresses:
  A: 0x7f32ade00000
  B: 0x7f32b2800000
  C: 0x7f32b2a00000
Capturing CUDA Graph...
Graph capture+instantiate time: 459us
Executing captured Graph...
Phase 1: Graph execution matches direct execution
 
--- Phase 2: Data Switching and Graph Update Check ---
Switching datasets while keeping virtual addresses unchanged...
Mapped physical memory to VA: 0x7f32ade00000
Mapped physical memory to VA: 0x7f32b2800000
Virtual address verification:
  A: 0x7f32ade00000 -> 0x7f32ade00000 (same: YES)
  B: 0x7f32b2800000 -> 0x7f32b2800000 (same: YES)
 
Capturing new graph with updated data...
New graph captured successfully
 
Checking if existing graph_exec can be updated with new graph...
Update check completed in 5us
Update result: Success (code: 0)
 
cudaGraphExecUpdate SUCCESS!
Meaning: The existing graph_exec can handle the new data without recompilation.
Reason: Only memory content changed, addresses remain identical.
 
Reusing existing graph_exec with new data...
Graph reuse execution time: 20us
 
Verifying results with new data...
Phase 2: Results are correct
 
Data change verification:
  Phase 1 result sum (first 10): 41880
  Phase 2 result sum (first 10): 365409
  Difference: 323529
Confirmed: Computation used new dataset
Graph successfully reused: YES
 
Demo completed successfully!

Graph View