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

Zi Yan
2016-09-26T15:38:12Z

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On 26 Sep 2016, at 11:22, zi.yan@sent.com wrote:

> From: Zi Yan <zi.yan@cs.rutgers.edu>
>
> 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.

Sorry, in ppc64, 64KB page was used as the base page and 16MB THP
was used.

>
> 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
> respectively.
>
> 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

And the BW number should be:
| 512 4KB pages | 1 2MB THP | 1 4KB page
x86_64 | 0.98GB/s | 2.97GB/s | 0.06GB/s

| 512 64KB pages | 1 16MB THP | 1 64KB page
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.
>
> Thanks,
> Zi Yan
> ---
>
> Naoya Horiguchi (11):
> mm: mempolicy: add queue_pages_node_check()
> mm: thp: introduce CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
> 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
> page
> 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(-)
>
> --
> 2.9.3
>
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--
Best Regards
Yan Zi

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