Am 25.05.2018 um 18:31 schrieb Ulrich Pegelow:
Am 25.05.2018 um 17:48 schrieb Matthias Bodenbinder:
Am 25.05.2018 um 14:35 schrieb Peter McD:
Is there a rule of thumb for headroom settings?
...
Specifically because I do not see a performance difference between
opencl_memory_headroom=1000 and opencl_memory_headroom=400. The
pipeline processing always takes the same time (with a 3 % variance).
So why shoulkd I bother with small values of opencl_memory_headroom?
In fact that depends a lot on your total amount of GPU memory.
When darktable's opencl support was implemented, systems with 1GB were
the norm. Typically only about 700MB of that would be available to
darktable, the rest needed to be left alone for system purposes (which
we found out by trial and error).
There were two corner cases to be taken into account:
* a too small value of opencl_memory_headroom would lead to out of
memory situations in darktable, processing would fall back to the CPU
which tends to be much slower.
* a too high value of opencl_memory_headroom would force darktable to go
into tile-wise processing much too often. This also costs performance.
As a reasonable compromise we now have a setting of 400 as default. That
should reserve enough space for the system and still prevent tiling in
most cases. ...
OK, I'll set headroom to 400 and see what will happen with my AMD
RX-460, 2GB memory.
Thank's
Peter
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