• Dan Williams's avatar
    mm: ZONE_DEVICE for "device memory" · 033fbae9
    Dan Williams authored
    While pmem is usable as a block device or via DAX mappings to userspace
    there are several usage scenarios that can not target pmem due to its
    lack of struct page coverage. In preparation for "hot plugging" pmem
    into the vmemmap add ZONE_DEVICE as a new zone to tag these pages
    separately from the ones that are subject to standard page allocations.
    Importantly "device memory" can be removed at will by userspace
    unbinding the driver of the device.
    
    Having a separate zone prevents allocation and otherwise marks these
    pages that are distinct from typical uniform memory.  Device memory has
    different lifetime and performance characteristics than RAM.  However,
    since we have run out of ZONES_SHIFT bits this functionality currently
    depends on sacrificing ZONE_DMA.
    
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Mel Gorman <mgorman@suse.de>
    Cc: Jerome Glisse <j.glisse@gmail.com>
    [hch: various simplifications in the arch interface]
    Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
    Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
    033fbae9
memory_hotplug.h 8.2 KB