[Beignet] Shared Host Memory but not Share

[Gao, Sanshan]

Hi, alls,


I want to use CL_MEM_USE_HOST_PTR to create a buffer object which shares host memory, so the changes to the elements in kernel can be used by host program.


But the result is that, I have changed the element in kernel, but the element in host program has not changed. I don't know why? Does this method still be a copy of host memory, so the change is not done to the host memory, but only device memory?


Hope for helps!


Device: GIGA Mini PC with core i7 and Iris Pro, integrated GPU
Kernel function:
 47 __kernel void PacketsIndexCalculation(
 48                          const unsigned int     packets_info_size,
 49                          __global packet_info_t  *packets_info,
 50                          const unsigned int     flow_table_size )
 51 {
 52     int gid = get_global_id(0);
 53     __global packet_info_t *p = packets_info + gid;
 54
 55     //calculate hash value
 56     p->index = ( ((p->flow_id).src_ip & 0xff) | (((p->flow_id).dst_ip & 0xff)<<8) |
 57                  (((p->flow_id).src_port & 0xff)<<16) | (((p->flow_id).dst_port & 0xff)<<24) )%flow_table_size;
 58    
 59 }
Problem:
 In host program, the memory pointed by &(p->index) has not changed by kernel function.











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