Re: Interacting with coherent memory on external devices

[Benjamin Herrenschmidt]

On Thu, 2015-04-23 at 09:10 -0500, Christoph Lameter wrote:
> On Thu, 23 Apr 2015, Benjamin Herrenschmidt wrote:
> 
> > >  Anyone
> > > wanting performance (and that is the prime reason to use a GPU) would
> > > switch this off because the latencies are otherwise not controllable and
> > > those may impact performance severely. There are typically multiple
> > > parallel strands of executing that must execute with similar performance
> > > in order to allow a data exchange at defined intervals. That is no longer
> > > possible if you add variances that come with the "transparency" here.
> >
> > Stop trying to apply your unique usage model to the entire world :-)
> 
> Much of the HPC apps that the world is using is severely impacted by what
> you are proposing. Its the industries usage model not mine. That is why I
> was asking about the use case. Does not seem to fit the industry you are
> targeting. This is also the basic design principle that got GPUs to work
> as fast as they do today. Introducing random memory latencies there will
> kill much of the benefit of GPUs there too.

How would it be impacted ? You can still do dedicated allocations etc...
if you want to do so. I think Jerome gave a pretty good explanation of
the need for the usage model we are proposing, it's also coming from the
industry ...

Ben.


> 
> 
> 
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