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SubjectRe: [LSF/MM TOPIC] NUMA, memory hierarchy and device memory

I see that the schedule is not full yet for the mm track and i would
really like to be able to have a discussion on this topic


On Fri, Jan 18, 2019 at 12:45:13PM -0500, Jerome Glisse wrote:
> Hi, i would like to discuss about NUMA API and its short comings when
> it comes to memory hierarchy (from fast HBM, to slower persistent
> memory through regular memory) and also device memory (which can have
> its own hierarchy).
> I have proposed a patch to add a new memory topology model to the
> kernel for application to be able to get that informations, it
> also included a set of new API to bind/migrate process range [1].
> Note that this model also support device memory.
> So far device memory support is achieve through device specific ioctl
> and this forbid some scenario like device memory interleaving accross
> multiple devices for a range. It also make the whole userspace more
> complex as program have to mix and match multiple device specific API
> on top of NUMA API.
> While memory hierarchy can be more or less expose through the existing
> NUMA API by creating node for non-regular memory [2], i do not see this
> as a satisfying solution. Moreover such scheme does not work for device
> memory that might not even be accessible by CPUs.
> Hence i would like to discuss few points:
> - What proof people wants to see this as problem we need to solve ?
> - How to build concensus to move forward on this ?
> - What kind of syscall API people would like to see ?
> People to discuss this topic:
> Dan Williams <>
> Dave Hansen <>
> Felix Kuehling <>
> John Hubbard <>
> Jonathan Cameron <>
> Keith Busch <>
> Mel Gorman <>
> Michal Hocko <>
> Paul Blinzer <>
> Probably others, sorry if i miss anyone from previous discussions.
> Cheers,
> Jérôme
> [1]
> [2]

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