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boxerab
Challenger
‎12-18-2016 04:55 PM

Strange clEnqueueMapImage/clEnqueueUnmapMemObject behaviour

Windows 10

Latest Crimson Driver

RX 470

I created a 1024x1024 image and mapped it with the CL_MAP_WRITE flag,

but I only mapped a 64x64 region in the image.

Using the returned pointer, I filled the entire 1024x1024 image , and called clEnqueueUnmapMemObject.

I expected only the 64x64 region to be copied from host to device, but in fact the entire 1024x1024 region gets copied.

Is this expected behaviour ? This doesn't seem very efficient to me: if I only map a 64x64 region, then only this region

should get copied to the card.

Thanks,

Aaron

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1 Solution
dipak
In response to boxerab
Big Boss
‎01-12-2017 06:11 AM

Hi Aaron,

The difference in behaviour looks an expected one. As I've come to know, though both types use pinned host memory, current implementation of CL_MEM_USE_HOST_PTR is little bit different than CL_MEM_ALLOC_HOST_PTR because of some alignments requirements. This may change in future.

Regards,

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