On Saturday, 17 August 2013 at 20:17:17 UTC, Atash wrote:
On Saturday, 17 August 2013 at 15:37:58 UTC, deadalnix wrote:
Unified memory have too much benefice for it to be ignored.
The open questions are about cache coherency, direct
communication between chips, identical performances through
the address space, and so on. But the unified memory will
remains. Even when memory is physically separated, you'll see
an unified memory model emerge, with disparate performances
depending on address space.
I'm not saying 'ignore it', I'm saying that it's not the least
common denominator among popular devices, and that in all
likelihood it won't be the least common denominator among
compute devices ever. AMD/ATi being 'right' doesn't mean that
they'll dominate the whole market. Having two slots on your
mobo is more limiting than having the ability to just chuck
more computers in a line hidden behind some thin wrapper around
some code built to deal with non-uniform memory access.
Additionally, in another post, I tried to demonstrate a way for
it to target the least common denominator, and in my (obviously
biased) opinion, it didn't look half bad.
Unlike uniform memory access, non-uniform memory access will
*always* be a thing. Uniform memory access is cool n'all, but
it isn't popular enough to be here now, and it isn't like
non-uniform memory access which has a long history of being
here and looks like it has a permanent stay in computing.
Pragmatism dictates to me here that any tool we want to be
'awesome', eliciting 'wowzers' from all the folk of the land,
should target the widest variety of devices while still being
pleasant to work with. *That* tells me that it is paramount to
*not* brush off non-uniform access, and that because
non-uniform access is the least common denominator, that should
be what is targeted.
On the other hand, if we want to start up some sort of thing
where one lib handles the paradigm of uniform memory access in
as convenient a way as possible, and another lib handles
non-uniform memory access, that's fine too. Except that the
first lib really would just be a specialization of the second
alongside some more 'convenience'-functions.
There are two major things, unified memory, and unified virtual
address space.
Unified virtual address will be universal within a few years, and
the user space application will no longer manage the cpu/gpu
copies anymore, this instead will be handled by the gpu system
library, hMMU, and operating system.
Even non-uniform memory will be uniform from the perspective of
the application writer.
