Use stricter host buffer alignment (64B) required by modern CPUs.

[pioto1225]

No description provided.

[pioto1225]

Hi,

Current clpeak does not show full D2H transfer potential of Arc GPU due to stricter alignment requirements on the host.
Using Core Ultra 9 285k Arc 770 is struggling to achieve any reasonable D2H bandwidth (1.6GBps) 14th gen Raptor-lake was better but still subpar (8GBps):

$ ./clpeak --transfer-bandwidth

Platform: Intel(R) OpenCL Graphics
  Device: Intel(R) Arc(TM) A770 Graphics
    Driver version  : 24.39.31294.12 (Linux x64)
    Compute units   : 512
    Clock frequency : 2400 MHz

    Transfer bandwidth (GBPS)
      enqueueWriteBuffer              : 20.25
      enqueueReadBuffer               : 1.69
      enqueueWriteBuffer non-blocking : 21.28
      enqueueReadBuffer non-blocking  : ^C

With the fix:

$ ./clpeak --transfer-bandwidth

Platform: Intel(R) OpenCL Graphics
  Device: Intel(R) Arc(TM) A770 Graphics
    Driver version  : 24.39.31294.12 (Linux x64)
    Compute units   : 512
    Clock frequency : 2400 MHz

    Transfer bandwidth (GBPS)
      enqueueWriteBuffer              : 20.58
      enqueueReadBuffer               : 21.01
      enqueueWriteBuffer non-blocking : 21.86
      enqueueReadBuffer non-blocking  : 22.39
      enqueueMapBuffer(for read)      : 20.38
        memcpy from mapped ptr        : 26.46
      enqueueUnmap(after write)       : 21.94
        memcpy to mapped ptr          : 27.08

For more information please refer to: intel/compute-runtime#775
Please consider merging.

[krrishnarraj]

Thanks for the find