• Dan Williams's avatar
    acpi/nfit, device-dax: Identify differentiated memory with a unique numa-node · 8fc5c735
    Dan Williams authored
    Persistent memory, as described by the ACPI NFIT (NVDIMM Firmware
    Interface Table), is the first known instance of a memory range
    described by a unique "target" proximity domain. Where "initiator" and
    "target" proximity domains is an approach that the ACPI HMAT
    (Heterogeneous Memory Attributes Table) uses to described the unique
    performance properties of a memory range relative to a given initiator
    (e.g. CPU or DMA device).
    Currently the numa-node for a /dev/pmemX block-device or /dev/daxX.Y
    char-device follows the traditional notion of 'numa-node' where the
    attribute conveys the closest online numa-node. That numa-node attribute
    is useful for cpu-binding and memory-binding processes *near* the
    device. However, when the memory range backing a 'pmem', or 'dax' device
    is onlined (memory hot-add) the memory-only-numa-node representing that
    address needs to be differentiated from the set of online nodes. In
    other words, the numa-node association of the device depends on whether
    you can bind processes *near* the cpu-numa-node in the offline
    device-case, or bind process *on* the memory-range directly after the
    backing address range is onlined.
    Allow for the case that platform firmware describes persistent memory
    with a unique proximity domain, i.e. when it is distinct from the
    proximity of DRAM and CPUs that are on the same socket. Plumb the Linux
    numa-node translation of that proximity through the libnvdimm region
    device to namespaces that are in device-dax mode. With this in place the
    proposed kmem driver [1] can optionally discover a unique numa-node
    number for the address range as it transitions the memory from an
    offline state managed by a device-driver to an online memory range
    managed by the core-mm.
    [1]: https://lore.kernel.org/lkml/20181022201317.8558C1D8@viggo.jf.intel.comReported-by: default avatarFan Du <fan.du@intel.com>
    Cc: Michael Ellerman <mpe@ellerman.id.au>
    Cc: "Oliver O'Halloran" <oohall@gmail.com>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: Jérôme Glisse <jglisse@redhat.com>
    Reviewed-by: default avatarYang Shi <yang.shi@linux.alibaba.com>
    Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
bus.h 1.8 KB