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What "cache hit %" shows on cacheless devices?

Question asked by Raistmer on Jul 18, 2014

First of all I would thank CodeXL developer team for improvements they make in Code XL 1.4. Now it's much more convenient tool.

 

Now the question:

On Loveland device there is no cache at all accordingly CLinfo-like enumerating:

 

OpenCL Platform Name: AMD Accelerated Parallel Processing
Number of devices: 1
  Max compute units: 2
  Max work group size: 256
  Max clock frequency: 275Mhz
  Max memory allocation: 175374336
  Cache type: None
  Cache line size: 0
  Cache size: 0
  Global memory size: 701497344
  Constant buffer size: 65536
  Max number of constant args: 8
  Local memory type: Scratchpad
  Local memory size: 32768
  Queue properties:
    Out-of-Order: No
  Name: Loveland
  Vendor: Advanced Micro Devices, Inc.
  Driver version: 1268.1 (VM)
  Version: OpenCL 1.2 AMD-APP (1268.1)
  Extensions: cl_khr_global_int32_base_atomics cl_khr_global_int32_extended_atomics cl_khr_local_int32_base_atomics cl_khr_local_int32_extended_atomics cl_khr_3d_image_writes cl_khr_byte_addressable_store cl_khr_gl_sharing cl_ext_atomic_counters_32 cl_amd_device_attribute_query cl_amd_vec3 cl_amd_printf cl_amd_media_ops cl_amd_media_ops2 cl_amd_popcnt cl_khr_d3d10_sharing cl_khr_dx9_media_sharing cl_amd_image2d_from_buffer_read_only

 

But CodeXL still shows cache hit %, for example:

Method, ExecutionOrder, ThreadID, CallIndex, GlobalWorkSize, WorkGroupSize, Time, LocalMemSize, VGPRs, SGPRs, ScratchRegs, FCStacks, KernelOccupancy, Wavefronts, LDSFetchInsts, LDSWriteInsts, FetchSize, CacheHit (%), FetchUnitBusy (%), FetchUnitStalled (%), WriteUnitStalled (%), FastPath, PathUtilization (%), LDSBankConflict (%)

GPU_fetch_array_kernel_twin_1D_persistent_cl__k12_Loveland1, 1540, 548, 9609, {    512       1       1}, {  256     1     1}, 436.32020, 32768, 30, NA, 0, 4, 12.5, 16, 87245.63, 32, 193527.63, 13.31, 30.87, 0.01, 1.75, 0, 0, 0

 

What its meaning then? Or OpenCL device capabilities quering returns wrong data and Loveland (C-60) device has cache? Please make some comments on this.

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