cancel
Showing results for 
Search instead for 
Did you mean: 

Archives Discussions

maximmoroz
Journeyman III

CL_DEVICE_GLOBAL_MEM_SIZE reduced in 11.6

Catalyst 11.6 is a really strange release.

I have 6950 equipped with 2GB of RAM. Up until 11.6 CL_DEVICE_GLOBAL_MEM_SIZE was always 1GB which is one half of available RAM. But now with 11.6 the global memory size for the device is 838860800 bytes, that is 800MB. CL_DEVICE_MAX_MEM_ALLOC_SIZE is reduces in the same degree.

I understand that AMD is free to change these values as far as they fit into OpenCL requirements. But I wonder why is only 39% of RAM available to OpenCL buffers?

0 Likes
9 Replies
rick_weber
Adept II

You can still get more memory usage if you use images in addition to global memory (or even just images).

0 Likes

Thanks, Rick. But it's kind of awckward workaround. Like it was with "use images in order to get cached reads". Now we have cached reads from const restrict buffers.

0 Likes

export GPU_MAX_ALLOC_PERCENT=100 - get all 2GB

0 Likes

I searched for the GPU_MAX_ALLOC_PERCENT and found just one page: http://forums.amd.com/devforum/textthread.cfm?catid=390&threadid=149197

It seems that it works only formally. Yes, you will be able to allocate buffers up to that limit, but the device memory usage remains the same - the surplus buffers are swapped to host memory. And the solution seems for Unix only.

0 Likes

i Windows takzhe, tol?ko ne "eksport" a v sistemnye peremennye, znachenie 1... YA v rabote ne proveryal no clinfo i AIDA64 raportovali o dostupnosti vsego ob?ema pamyati

0 Likes

no this enviroment variables shold work on windows too. but they are just too unreliable.

0 Likes

Originally posted by: ED1980 i Windows takzhe, tol?ko ne "eksport" a v sistemnye peremennye, znachenie 1... YA v rabote ne proveryal no clinfo i AIDA64 raportovali o dostupnosti vsego ob?ema pamyati

Well, the question is not how to hack it. For my goals even 250MB is more than enough. But I wonder why only 39% of device RAM is available to OpenCL runtime while there are people who are asking for 1GB of  CL_DEVICE_MAX_MEM_ALLOC_SIZE.

0 Likes

This is strange of course, I would have understood if the needs of the graphics (showing desktop) has been reserved a specific amount of memory, say 50 ~ 100 megabytes, but half or more, especially in the case of video cards have 1 - 2 gigabytes of memory, it is pointless

0 Likes

Yep, agree. NVidia does this way (soem megabytes reserved for video-buffer).

0 Likes