Cliff note: HMM offers 2 things (each standing on its own). First
it allows to use device memory transparently inside any process
without any modifications to process program code. Second it allows
to mirror process address space on a device.
Change since v12 is the use of struct page for device memory even if
the device memory is not accessible by the CPU (because of limitation
impose by the bus between the CPU and the device).
Using struct page means that their are minimal changes to core mm
code. HMM build on top of ZONE_DEVICE to provide struct page, it
adds new features to ZONE_DEVICE. The first 7 patches implement
those changes.
Rest of patchset is divided into 3 features that can each be use
independently from one another. First is the process address space
mirroring (patch 9 to 13), this allow to snapshot CPU page table
and to keep the device page table synchronize with the CPU one.
Second is a new memory migration helper which allow migration of
a range of virtual address of a process. This memory migration
also allow device to use their own DMA engine to perform the copy
between the source memory and destination memory. This can be
usefull even outside HMM context in many usecase.
Third part of the patchset (patch 17-18) is a set of helper to
register a ZONE_DEVICE node and manage it. It is meant as a
convenient helper so that device drivers do not each have to
reimplement over and over the same boiler plate code.
I am hoping that this can now be consider for inclusion upstream.
Bottom line is that without HMM we can not support some of the new
hardware features on x86 PCIE. I do believe we need some solution
to support those features or we won't be able to use such hardware
in standard like C++17, OpenCL 3.0 and others.
I have been working with NVidia to bring up this feature on their
Pascal GPU. There are real hardware that you can buy today that
could benefit from HMM. We also intend to leverage this inside the
open source nouveau driver.
In this patchset i restricted myself to set of core features what
is missing:
- force read only on CPU for memory duplication and GPU atomic
- changes to mmu_notifier for optimization purposes
- migration of file back page to device memory
I plan to submit a couple more patchset to implement those feature
once core HMM is upstream.
Is there anything blocking HMM inclusion ? Something fundamental ?
Previous patchset posting :
v1 http://lwn.net/Articles/597289/
v2 https://lkml.org/lkml/2014/6/12/559
v3 https://lkml.org/lkml/2014/6/13/633
v4 https://lkml.org/lkml/2014/8/29/423
v5 https://lkml.org/lkml/2014/11/3/759
v6 http://lwn.net/Articles/619737/
v7 http://lwn.net/Articles/627316/
v8 https://lwn.net/Articles/645515/
v9 https://lwn.net/Articles/651553/
v10 https://lwn.net/Articles/654430/
v11 http://www.gossamer-threads.com/lists/linux/kernel/2286424
v12 http://www.kernelhub.org/?msg=972982&p=2
Cheers,
Jérôme
Jérôme Glisse (18):
mm/memory/hotplug: convert device parameter bool to set of flags
mm/ZONE_DEVICE/unaddressable: add support for un-addressable device
memory
mm/ZONE_DEVICE/free_hot_cold_page: catch ZONE_DEVICE pages
mm/ZONE_DEVICE/free-page: callback when page is freed
mm/ZONE_DEVICE/devmem_pages_remove: allow early removal of device
memory
mm/ZONE_DEVICE/unaddressable: add special swap for unaddressable
mm/ZONE_DEVICE/x86: add support for un-addressable device memory
mm/hmm: heterogeneous memory management (HMM for short)
mm/hmm/mirror: mirror process address space on device with HMM helpers
mm/hmm/mirror: add range lock helper, prevent CPU page table update
for the range
mm/hmm/mirror: add range monitor helper, to monitor CPU page table
update
mm/hmm/mirror: helper to snapshot CPU page table
mm/hmm/mirror: device page fault handler
mm/hmm/migrate: support un-addressable ZONE_DEVICE page in migration
mm/hmm/migrate: add new boolean copy flag to migratepage() callback
mm/hmm/migrate: new memory migration helper for use with device memory
mm/hmm/devmem: device driver helper to hotplug ZONE_DEVICE memory
mm/hmm/devmem: dummy HMM device as an helper for ZONE_DEVICE memory
MAINTAINERS | 7 +
arch/ia64/mm/init.c | 19 +-
arch/powerpc/mm/mem.c | 18 +-
arch/s390/mm/init.c | 10 +-
arch/sh/mm/init.c | 18 +-
arch/tile/mm/init.c | 10 +-
arch/x86/mm/init_32.c | 19 +-
arch/x86/mm/init_64.c | 23 +-
drivers/dax/pmem.c | 3 +-
drivers/nvdimm/pmem.c | 5 +-
drivers/staging/lustre/lustre/llite/rw26.c | 8 +-
fs/aio.c | 7 +-
fs/btrfs/disk-io.c | 11 +-
fs/hugetlbfs/inode.c | 9 +-
fs/nfs/internal.h | 5 +-
fs/nfs/write.c | 9 +-
fs/proc/task_mmu.c | 10 +-
fs/ubifs/file.c | 8 +-
include/linux/balloon_compaction.h | 3 +-
include/linux/fs.h | 13 +-
include/linux/hmm.h | 516 ++++++++++++
include/linux/memory_hotplug.h | 17 +-
include/linux/memremap.h | 39 +-
include/linux/migrate.h | 7 +-
include/linux/mm_types.h | 5 +
include/linux/swap.h | 18 +-
include/linux/swapops.h | 67 ++
kernel/fork.c | 2 +
kernel/memremap.c | 48 +-
mm/Kconfig | 23 +
mm/Makefile | 1 +
mm/balloon_compaction.c | 2 +-
mm/hmm.c | 1175 ++++++++++++++++++++++++++++
mm/memory.c | 33 +
mm/memory_hotplug.c | 4 +-
mm/migrate.c | 651 ++++++++++++++-
mm/mprotect.c | 12 +
mm/page_alloc.c | 10 +
mm/rmap.c | 47 ++
tools/testing/nvdimm/test/iomap.c | 2 +-
40 files changed, 2811 insertions(+), 83 deletions(-)
create mode 100644 include/linux/hmm.h
create mode 100644 mm/hmm.c
--
2.4.3
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