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Thread: OpenCL rectangular-copy function is either slow or crashes on a AMD machine

  1. #1
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    OpenCL rectangular-copy function is either slow or crashes on a AMD machine

    The clinfo output from our AMD machine, containing AMD Firepro V4800 as a discrete GPU, can be found in the next post.

    The OpenCL rectangular copy function crashes when CPU is used as an OpenCL device on the AMD Fusion APU.
    Is there any way to workaround this?

    Rectangular-copy from GPU to CPU of data which is not contiguous in memory is very slow. For a rectangle of size 4096x4096, copying the data if it is not contiguous in memory takes 6.7 times the time taken to copy the data when it is contiguous in memory. A similar ratio on our NVIDIA Tesla C2050 machine is 1.34.
    The results (on NVIDIA Tesla C2050 and AMD Firepro V4800) comparing the performance of rectangular-copy from GPU to CPU for different rectangle sizes, when the data to be copied is contiguous in memory and when it is not, can be found here:
    https://docs.google.com/spreadsheet/...zdnJ1RGc#gid=0
    The performance of rectangular-copy from CPU to GPU is similar.

    What is the reason for such a huge slowdown in rectangular-copy from GPU to CPU when the data to be copied is not contiguous in memory? The motivation behind using a rectangular-copy is to avoid such a huge slowdown.
    Are there any ways in which we can overcome this? Can we improve the performance of copying non-contiguous memory from GPU to CPU (and from CPU to GPU) in some way?

    - - - Updated - - -

    The clinfo output from our AMD machine, containing AMD Firepro V4800 as a discrete GPU:

    Number of platforms: 1
    Platform Profile: FULL_PROFILE
    Platform Version: OpenCL 1.2 AMD-APP (938.2)
    Platform Name: AMD Accelerated Parallel Processing
    Platform Vendor: Advanced Micro Devices, Inc.
    Platform Extensions: cl_khr_icd cl_amd_event_callback cl_amd_offline_devices


    Platform Name: AMD Accelerated Parallel Processing
    Number of devices: 4
    Device Type: CL_DEVICE_TYPE_GPU
    Device ID: 4098
    Board name: AMD Radeon HD 6550D
    Device Topology: PCI[ B#0, D#1, F#0 ]
    Max compute units: 5
    Max work items dimensions: 3
    Max work items[0]: 256
    Max work items[1]: 256
    Max work items[2]: 256
    Max work group size: 256
    Preferred vector width char: 16
    Preferred vector width short: 8
    Preferred vector width int: 4
    Preferred vector width long: 2
    Preferred vector width float: 4
    Preferred vector width double: 0
    Native vector width char: 16
    Native vector width short: 8
    Native vector width int: 4
    Native vector width long: 2
    Native vector width float: 4
    Native vector width double: 0
    Max clock frequency: 0Mhz
    Address bits: 32
    Max memory allocation: 536870912
    Image support: Yes
    Max number of images read arguments: 128
    Max number of images write arguments: 8
    Max image 2D width: 8192
    Max image 2D height: 8192
    Max image 3D width: 2048
    Max image 3D height: 2048
    Max image 3D depth: 2048
    Max samplers within kernel: 16
    Max size of kernel argument: 1024
    Alignment (bits) of base address: 2048
    Minimum alignment (bytes) for any datatype: 128
    Single precision floating point capability
    Denorms: No
    Quiet NaNs: Yes
    Round to nearest even: Yes
    Round to zero: Yes
    Round to +ve and infinity: Yes
    IEEE754-2008 fused multiply-add: Yes
    Cache type: None
    Cache line size: 0
    Cache size: 0
    Global memory size: 536870912
    Constant buffer size: 65536
    Max number of constant args: 8
    Local memory type: Scratchpad
    Local memory size: 32768
    Kernel Preferred work group size multiple: 64
    Error correction support: 0
    Unified memory for Host and Device: 1
    Profiling timer resolution: 1
    Device endianess: Little
    Available: Yes
    Compiler available: Yes
    Execution capabilities:
    Execute OpenCL kernels: Yes
    Execute native function: No
    Queue properties:
    Out-of-Order: No
    Profiling : Yes
    Platform ID: 0x7f07dc0c6ce0
    Name: BeaverCreek
    Vendor: Advanced Micro Devices, Inc.
    Device OpenCL C version: OpenCL C 1.2
    Driver version: CAL 1.4.1741
    Profile: FULL_PROFILE
    Version: OpenCL 1.2 AMD-APP (938.2)
    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_popcnt


    Device Type: CL_DEVICE_TYPE_GPU
    Device ID: 4098
    Board name: ATI FirePro V4800 (FireGL)
    Device Topology: PCI[ B#1, D#0, F#0 ]
    Max compute units: 5
    Max work items dimensions: 3
    Max work items[0]: 256
    Max work items[1]: 256
    Max work items[2]: 256
    Max work group size: 256
    Preferred vector width char: 16
    Preferred vector width short: 8
    Preferred vector width int: 4
    Preferred vector width long: 2
    Preferred vector width float: 4
    Preferred vector width double: 0
    Native vector width char: 16
    Native vector width short: 8
    Native vector width int: 4
    Native vector width long: 2
    Native vector width float: 4
    Native vector width double: 0
    Max clock frequency: 0Mhz
    Address bits: 32
    Max memory allocation: 1073741824
    Image support: Yes
    Max number of images read arguments: 128
    Max number of images write arguments: 8
    Max image 2D width: 8192
    Max image 2D height: 8192
    Max image 3D width: 2048
    Max image 3D height: 2048
    Max image 3D depth: 2048
    Max samplers within kernel: 16
    Max size of kernel argument: 1024
    Alignment (bits) of base address: 2048
    Minimum alignment (bytes) for any datatype: 128
    Single precision floating point capability
    Denorms: No
    Quiet NaNs: Yes
    Round to nearest even: Yes
    Round to zero: Yes
    Round to +ve and infinity: Yes
    IEEE754-2008 fused multiply-add: Yes
    Cache type: None
    Cache line size: 0
    Cache size: 0
    Global memory size: 1073741824
    Constant buffer size: 65536
    Max number of constant args: 8
    Local memory type: Scratchpad
    Local memory size: 32768
    Kernel Preferred work group size multiple: 64
    Error correction support: 0
    Unified memory for Host and Device: 0
    Profiling timer resolution: 1
    Device endianess: Little
    Available: Yes
    Compiler available: Yes
    Execution capabilities:
    Execute OpenCL kernels: Yes
    Execute native function: No
    Queue properties:
    Out-of-Order: No
    Profiling : Yes
    Platform ID: 0x7f07dc0c6ce0
    Name: Redwood
    Vendor: Advanced Micro Devices, Inc.
    Device OpenCL C version: OpenCL C 1.2
    Driver version: CAL 1.4.1741
    Profile: FULL_PROFILE
    Version: OpenCL 1.2 AMD-APP (938.2)
    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_popcnt
    Last edited by roshan; 06-14-2013 at 04:38 AM.

  2. #2
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    Jun 2013
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    2
    Device Type: CL_DEVICE_TYPE_GPU
    Device ID: 4098
    Board name: ATI FirePro V4800 (FireGL)
    Device Topology: PCI[ B#2, D#0, F#0 ]
    Max compute units: 5
    Max work items dimensions: 3
    Max work items[0]: 256
    Max work items[1]: 256
    Max work items[2]: 256
    Max work group size: 256
    Preferred vector width char: 16
    Preferred vector width short: 8
    Preferred vector width int: 4
    Preferred vector width long: 2
    Preferred vector width float: 4
    Preferred vector width double: 0
    Native vector width char: 16
    Native vector width short: 8
    Native vector width int: 4
    Native vector width long: 2
    Native vector width float: 4
    Native vector width double: 0
    Max clock frequency: 0Mhz
    Address bits: 32
    Max memory allocation: 1073741824
    Image support: Yes
    Max number of images read arguments: 128
    Max number of images write arguments: 8
    Max image 2D width: 8192
    Max image 2D height: 8192
    Max image 3D width: 2048
    Max image 3D height: 2048
    Max image 3D depth: 2048
    Max samplers within kernel: 16
    Max size of kernel argument: 1024
    Alignment (bits) of base address: 2048
    Minimum alignment (bytes) for any datatype: 128
    Single precision floating point capability
    Denorms: No
    Quiet NaNs: Yes
    Round to nearest even: Yes
    Round to zero: Yes
    Round to +ve and infinity: Yes
    IEEE754-2008 fused multiply-add: Yes
    Cache type: None
    Cache line size: 0
    Cache size: 0
    Global memory size: 1073741824
    Constant buffer size: 65536
    Max number of constant args: 8
    Local memory type: Scratchpad
    Local memory size: 32768
    Kernel Preferred work group size multiple: 64
    Error correction support: 0
    Unified memory for Host and Device: 0
    Profiling timer resolution: 1
    Device endianess: Little
    Available: Yes
    Compiler available: Yes
    Execution capabilities:
    Execute OpenCL kernels: Yes
    Execute native function: No
    Queue properties:
    Out-of-Order: No
    Profiling : Yes
    Platform ID: 0x7f07dc0c6ce0
    Name: Redwood
    Vendor: Advanced Micro Devices, Inc.
    Device OpenCL C version: OpenCL C 1.2
    Driver version: CAL 1.4.1741
    Profile: FULL_PROFILE
    Version: OpenCL 1.2 AMD-APP (938.2)
    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_popcnt


    Device Type: CL_DEVICE_TYPE_CPU
    Device ID: 4098
    Board name:
    Max compute units: 4
    Max work items dimensions: 3
    Max work items[0]: 1024
    Max work items[1]: 1024
    Max work items[2]: 1024
    Max work group size: 1024
    Preferred vector width char: 16
    Preferred vector width short: 8
    Preferred vector width int: 4
    Preferred vector width long: 2
    Preferred vector width float: 4
    Preferred vector width double: 0
    Native vector width char: 16
    Native vector width short: 8
    Native vector width int: 4
    Native vector width long: 2
    Native vector width float: 4
    Native vector width double: 0
    Max clock frequency: 800Mhz
    Address bits: 64
    Max memory allocation: 2147483648
    Image support: Yes
    Max number of images read arguments: 128
    Max number of images write arguments: 8
    Max image 2D width: 8192
    Max image 2D height: 8192
    Max image 3D width: 2048
    Max image 3D height: 2048
    Max image 3D depth: 2048
    Max samplers within kernel: 16
    Max size of kernel argument: 4096
    Alignment (bits) of base address: 1024
    Minimum alignment (bytes) for any datatype: 128
    Single precision floating point capability
    Denorms: Yes
    Quiet NaNs: Yes
    Round to nearest even: Yes
    Round to zero: Yes
    Round to +ve and infinity: Yes
    IEEE754-2008 fused multiply-add: Yes
    Cache type: Read/Write
    Cache line size: 64
    Cache size: 65536
    Global memory size: 7838502912
    Constant buffer size: 65536
    Max number of constant args: 8
    Local memory type: Global
    Local memory size: 32768
    Kernel Preferred work group size multiple: 1
    Error correction support: 0
    Unified memory for Host and Device: 1
    Profiling timer resolution: 1
    Device endianess: Little
    Available: Yes
    Compiler available: Yes
    Execution capabilities:
    Execute OpenCL kernels: Yes
    Execute native function: Yes
    Queue properties:
    Out-of-Order: No
    Profiling : Yes
    Platform ID: 0x7f07dc0c6ce0
    Name: AMD A8-3850 APU with Radeon(tm) HD Graphics
    Vendor: AuthenticAMD
    Device OpenCL C version: OpenCL C 1.2
    Driver version: 2.0 (sse2)
    Profile: FULL_PROFILE
    Version: OpenCL 1.2 AMD-APP (938.2)
    Extensions: cl_khr_fp64 cl_amd_fp64 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_int64_base_atomics cl_khr_int64_extended_atomics cl_khr_byte_addressable_store cl_khr_gl_sharing cl_ext_device_fission cl_amd_device_attribute_query cl_amd_vec3 cl_amd_printf cl_amd_media_ops cl_amd_popcnt

  3. #3
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    Jun 2013
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    It's also odd that the difference between non-contiguous copy performance and contiguous one increases as the array size increases. With an increase in array size, larger contiguous portions need to be transferred (for eg., 4096 lines of 4096 contiguous elements for 4096x4096), and the gap is expected to reduce or remain the same.

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