Re: [Starpu-devel] Problems with memory in CUDA

[Samuel Thibault <samuel.thibault@ens-lyon.org>]

Cyril Bordage, le Mon 21 Oct 2013 02:09:45 +0200, a écrit :
> I call starpu_data_unregister_submit to free memory. It works well on
> CPUs, but only on CPUs, not on GPUs. To be more precise, I see, with
> nvidia-smi, only increasing in memory consumption. And it ends with a
> "error: out of memory". If I split my program into two passes, it works
> like a charm (no out of memory).

Well, it is expected that StarPU does not release memory immediately,
for two reasons:

- it releases GPU memory from the GPU-driving thread, not from the thread
making the free call. Releasing data is triggered when the GPU is low on
memory.  What is returning an out of memory error exactly?  That part
should be triggered releasing data, if it isn't there's a bug there.
- for GPUs there is an allocation cache, to allow free/alloc data
reuses.  Are your data all the same, or of varying sizes & types?  In
the latter case, the cache will not be very useful, but again, it should
get flushed on low memory condition.  You can try to avoid it completely
by passing --disable-allocation-cache to configure.

Samuel