[PATCH v1 00/12] mm: THP migration support

From: zi . yan
Date: Mon Sep 26 2016 - 11:24:04 EST

From: Zi Yan <zi.yan@xxxxxxxxxxxxxx>

Hi all,

This patchset is based on Naoya Horiguchi's page migration enchancement
for thp patchset with additional IBM ppc64 support. And I rebase it
on the latest upstream commit.

The motivation is that 4KB page migration is underutilizing the memory
bandwidth compared to 2MB THP migration.

As part of my internship work in NVIDIA, I compared the bandwidth
utilizations between 512 4KB pages and 1 2MB page in both x86_64 and ppc64.
And the results show that migrating 512 4KB pages takes only 3x and 1.15x of
the time, compared to migrating single 2MB THP, in x86_64 and ppc64

Here are the actual BW numbers (total_data_size/migration_time):
| 512 4KB pages | 1 2MB THP | 1 4KB page
x86_64 | 0.98GB/s | 2.97GB/s | 0.06GB/s
ppc64 | 6.14GB/s | 7.10GB/s | 1.24GB/s

Any comments or advices are welcome.

Here is the original message from Naoya:

This patchset enhances page migration functionality to handle thp migration
for various page migration's callers:
- mbind(2)
- move_pages(2)
- migrate_pages(2)
- cgroup/cpuset migration
- memory hotremove
- soft offline

The main benefit is that we can avoid unnecessary thp splits, which helps us
avoid performance decrease when your applications handles NUMA optimization on
their own.

The implementation is similar to that of normal page migration, the key point
is that we modify a pmd to a pmd migration entry in swap-entry like format.
pmd_present() is not simple and it's not enough by itself to determine whether
a given pmd is a pmd migration entry. See patch 3/11 and 5/11 for details.

Here're topics which might be helpful to start discussion:

- at this point, this functionality is limited to x86_64.

- there's alrealy an implementation of thp migration in autonuma code of which
this patchset doesn't touch anything because it works fine as it is.

- fallback to thp split: current implementation just fails a migration trial if
thp migration fails. It's possible to retry migration after splitting the thp,
but that's not included in this version.

Zi Yan

Naoya Horiguchi (11):
mm: mempolicy: add queue_pages_node_check()
mm: thp: add helpers related to thp/pmd migration
mm: thp: enable thp migration in generic path
mm: thp: check pmd migration entry in common path
mm: soft-dirty: keep soft-dirty bits over thp migration
mm: hwpoison: fix race between unpoisoning and freeing migrate source
mm: hwpoison: soft offline supports thp migration
mm: mempolicy: mbind and migrate_pages support thp migration
mm: migrate: move_pages() supports thp migration
mm: memory_hotplug: memory hotremove supports thp migration

Zi Yan (1):
mm: ppc64: Add THP migration support for ppc64.

arch/powerpc/Kconfig | 4 +
arch/powerpc/include/asm/book3s/64/pgtable.h | 23 ++++
arch/x86/Kconfig | 4 +
arch/x86/include/asm/pgtable.h | 28 ++++
arch/x86/include/asm/pgtable_64.h | 2 +
arch/x86/include/asm/pgtable_types.h | 8 +-
arch/x86/mm/gup.c | 3 +
fs/proc/task_mmu.c | 20 +--
include/asm-generic/pgtable.h | 34 ++++-
include/linux/huge_mm.h | 13 ++
include/linux/swapops.h | 64 ++++++++++
mm/Kconfig | 3 +
mm/gup.c | 8 ++
mm/huge_memory.c | 184 +++++++++++++++++++++++++--
mm/memcontrol.c | 2 +
mm/memory-failure.c | 41 +++---
mm/memory.c | 5 +
mm/memory_hotplug.c | 8 ++
mm/mempolicy.c | 108 ++++++++++++----
mm/migrate.c | 49 ++++++-
mm/page_isolation.c | 9 ++
mm/rmap.c | 5 +
22 files changed, 549 insertions(+), 76 deletions(-)