On Fri, 2017-05-05 at 13:48 -0400, Jerome Glisse wrote: > Well there is _no_ migration issues with HMM (anonymous or file back > pages). What you don't get is thing like lru or numa balancing but i > believe you do not want either of those anyway. We don't want them in the specific case of GPUs today for various reasons related more to how they are used and specific implementation shortcomings, so matter of policy. However, I don't think they are necessarily to be excluded in the grand scheme of things of coherent accelerators with local memory. So my gut feeling (but we can agree to disagree, in the end, what we need is *a* workable solution to enable these things, which ever it is that wins), is that we are better off simply treating them as normal numa nodes, and adding more policy tunables where needed, if possible with some of these being set to reasonable defaults by the driver itself to account for implementation shortcomings. Now, if Michal and Mel strongly prefer the approach based on HMM, we can make it work as well I believe. It feels less "natural" and more convoluted. That's it. This is by no mean a criticism of HMM btw :-) HMM still is a critical part of getting the non-coherent devices working properly, and which ever representation we use for the memory on the coherent ones, we will also use parts of HMM infrastructure for driver directed migration anyway. Cheers, Ben. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
