[Beignet] CL_MEM_USE_HOST_PTR involve extra copy?

[spring_wind]

You mean if I use CL_MEM_USE_HOST_PTR and host ptr is page aligned, I change the data pointed by host ptr from CPU side, I don't have to do any flush opertaion or I should still call clMapxx function?






在 2014-12-03 08:37:15，"Guo, Yejun" <yejun.guo at intel.com> 写道：


Hi,

 

please check the latest code of beignet, there is no copy needed between CPU and GPU if the host_ptr provided by application is page aligned, and the page align limitation is expected to be removed some days later. You can also try CL_MEM_ALLOC_HOST_PTR to avoid the extra copy without align limitation.

 

Btw, this zero-copy is supported starting from linux kernel 3.16 and libdrm 2.4.58.

 

 

From: Beignet [mailto:beignet-bounces at lists.freedesktop.org] On Behalf Of spring_wind
Sent: Tuesday, December 02, 2014 8:38 PM
To:beignet at lists.freedesktop.org
Subject: [Beignet] CL_MEM_USE_HOST_PTR involve extra copy?

 

Hi:

Intel opencl optimization guide said using CL_MEM_USE_HOST_PTR can avoid extra copy between CPU and GPU, but I noticed that in beignet's implementation source it was not like that:

/* Copy the data if required */

  if (flags & CL_MEM_COPY_HOST_PTR || flags & CL_MEM_USE_HOST_PTR)

    cl_buffer_subdata(mem->bo, 0, sz, data);

 

Could someone give me an answer?

 
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