On 01/06/2017 10:46 AM, Jérôme Glisse wrote: > This patch add a new memory migration helpers, which migrate memory > backing a range of virtual address of a process to different memory > (which can be allocated through special allocator). It differs from > numa migration by working on a range of virtual address and thus by > doing migration in chunk that can be large enough to use DMA engine > or special copy offloading engine. > > Expected users are any one with heterogeneous memory where different > memory have different characteristics (latency, bandwidth, ...). As > an example IBM platform with CAPI bus can make use of this feature > to migrate between regular memory and CAPI device memory. New CPU > architecture with a pool of high performance memory not manage as > cache but presented as regular memory (while being faster and with > lower latency than DDR) will also be prime user of this patch. Why should the normal page migration path (where neither src nor dest are device private), use the hmm_migrate functionality? 11-14 are replicating a lot of the normal migration functionality but with special casing for HMM requirements. When migrating THP's or a list of pages (your use case above), normal NUMA migration is going to want to do this as fast as possible too (see Zi Yan's patches for multi-threading normal migrations & prototype of using intel IOAT for transfers, he sees 3-5x speedup). If the intention is to provide a common interface hook for migration to use DMA acceleration (which is a good idea), it probably shouldn't be special cased inside HMM functionality. For example, using the intel IOAT for migration DMA has nothing to do with HMM whatsoever. We need a normal migration path interface to allow DMA that isn't tied to HMM. -- 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