omion

Questions about OpenCL programming guide

Discussion created by omion on Apr 26, 2011
Latest reply on May 2, 2011 by himanshu.gautam
Exact limits from section 4

In a number of places in the April 2011 version of the OpenCL programming guide there are references to "limited" memory, but I can't find anything saying exactly what those limits are.

1
4.4.1.3
The runtime allocates a limited amount of pinned host memory that is accessible by the GPU without using the CPU cache coherency protocol.


2
4.4.1.5
A limited portion of discrete GPU device memory is configured to be directly accessible by the CPU.


3
4.5.2.2
There is a limit on the maximum size per [zero-copy] buffer, as well as on the total size of all buffers. This is platform-dependent, limited in size for each buffer, and also for the total size of all buffers of that type (a good working assumption is 64 MB for the per-buffer limit, and 128 MB for the total).


I don't see anything about what those limits would depend on, or how to check what my system's limits are. 3 lists a "good working assumption" but it doesn't say why the limits would be any more or less than that.

Also, I haven't run into any actual limits on allocation testing out quotes 1 and 2. That leads me to believe that either the limits are larger than an allocatable buffer or that the system is silently using a different type of memory when those limits are reached.

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