Re: [HMM v17 00/14] HMM (Heterogeneous Memory Management) v17

From: John Hubbard
Date: Sat Jan 28 2017 - 00:39:51 EST

On 01/27/2017 02:52 PM, JÃrÃme Glisse wrote:
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 v16:
- move HMM unaddressable device memory to its own radix tree and
thus find_dev_pagemap() will no longer return HMM dev_pagemap
- rename HMM migration helper (drop the prefix) and make them
completely independent of HMM

Migration can now be use to implement thing like multi-threaded
copy or make use of specific memory allocator for destination
memory.

We're about to do our usual testing with this, but there will be a brief pause first (the driver API has changed slightly).

thanks
john h


Work is under way to use this feature inside nouveau (the upstream
open source driver for NVidia GPU) either 411 or 4.12 timeframe.
But this patchset have been otherwise tested with the close source
driver for NVidia GPU and thus we are confident it works and allow
to use the hardware for seamless interaction between CPU and GPU
in common address space of a process.

I also discussed the features with other company and i am confident
it can be use on other, yet, unrelease hardware.

Please condiser applying for 4.11


Know issues:

Device memory pick some random unuse physical address range. Latter
memory hotplug might fails because of this. Intention is to fix this
in latter patchset to use physical address above the platform limit
thus making sure that no real memory can be hotplug at conflicting
address.


Patchset overview:

Patchset is divided into 3 features that can each be use independently
from one another. First is changes to ZONE_DEVICE so we can have struct
page for device un-addressable memory (patch 1-4 and 13-14). Second is
process address space mirroring (patch 8 to 11), this allow to snapshot
CPU page table and to keep the device page table synchronize with the
CPU one.

Last is a new page migration helper which allow migration for range of
virtual address using hardware copy engine (patch 5-7 for new migrate
function and 12 for migration of un-addressable memory).


Future plan:

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 features
once core HMM is upstream.

Git tree:
https://cgit.freedesktop.org/~glisse/linux/log/?h=hmm-v17


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
v13 https://lwn.net/Articles/706856/
v14 https://lkml.org/lkml/2016/12/8/344
v15 http://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg1304107.html
v16 http://www.spinics.net/lists/linux-mm/msg119814.html

JÃrÃme Glisse (14):
mm/memory/hotplug: convert device bool to int to allow for more flags
v2
mm/ZONE_DEVICE/free-page: callback when page is freed v2
mm/ZONE_DEVICE/unaddressable: add support for un-addressable device
memory v3
mm/ZONE_DEVICE/x86: add support for un-addressable device memory
mm/migrate: add new boolean copy flag to migratepage() callback
mm/migrate: new memory migration helper for use with device memory v3
mm/migrate: migrate_vma() unmap page from vma while collecting pages
mm/hmm: heterogeneous memory management (HMM for short)
mm/hmm/mirror: mirror process address space on device with HMM helpers
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/devmem: device memory hotplug using ZONE_DEVICE
mm/hmm/devmem: dummy HMM device for ZONE_DEVICE memory v2

MAINTAINERS | 7 +
arch/ia64/mm/init.c | 23 +-
arch/powerpc/mm/mem.c | 22 +-
arch/s390/mm/init.c | 10 +-
arch/sh/mm/init.c | 22 +-
arch/tile/mm/init.c | 10 +-
arch/x86/mm/init_32.c | 23 +-
arch/x86/mm/init_64.c | 41 +-
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 | 464 +++++++++++
include/linux/ioport.h | 1 +
include/linux/memory_hotplug.h | 31 +-
include/linux/memremap.h | 39 +-
include/linux/migrate.h | 83 +-
include/linux/mm_types.h | 5 +
include/linux/swap.h | 18 +-
include/linux/swapops.h | 67 ++
kernel/fork.c | 2 +
kernel/memremap.c | 31 +-
mm/Kconfig | 38 +
mm/Makefile | 1 +
mm/balloon_compaction.c | 2 +-
mm/hmm.c | 1235 ++++++++++++++++++++++++++++
mm/memory.c | 64 +-
mm/memory_hotplug.c | 14 +-
mm/migrate.c | 659 ++++++++++++++-
mm/mprotect.c | 12 +
mm/rmap.c | 47 ++
mm/zsmalloc.c | 12 +-
38 files changed, 2986 insertions(+), 80 deletions(-)
create mode 100644 include/linux/hmm.h
create mode 100644 mm/hmm.c

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2.4.3