linux-kernel - Re: [RFC 0/4] mm/memblock: Skip prep and initialization of struct pages freed later by HVO

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Message-ID: <03476b1d-c825-0ab6-73bc-b98419d3dff6@bytedance.com>
Date:   Wed, 26 Jul 2023 11:34:14 +0100
From:   Usama Arif <usama.arif@...edance.com>
To:     linux-mm@...ck.org, muchun.song@...ux.dev, mike.kravetz@...cle.com,
        rppt@...nel.org
Cc:     linux-kernel@...r.kernel.org, fam.zheng@...edance.com,
        liangma@...ngbit.com, simon.evans@...edance.com,
        punit.agrawal@...edance.com
Subject: Re: [RFC 0/4] mm/memblock: Skip prep and initialization of struct
 pages freed later by HVO



On 24/07/2023 14:46, Usama Arif wrote:
> If the region is for gigantic hugepages and if HVO is enabled, then those
> struct pages which will be freed later by HVO don't need to be prepared and
> initialized. This can save significant time when a large number of hugepages
> are allocated at boot time.
> 
> For a 1G hugepage, this series avoid initialization and preparation of
> 262144 - 64 = 262080 struct pages per hugepage.
> 
> When tested on a 512G system (which can allocate max 500 1G hugepages), the
> kexec-boot time with HVO and DEFERRED_STRUCT_PAGE_INIT enabled without this
> patchseries to running init is 3.9 seconds. With this patch it is 1.2 seconds.
> This represents an approximately 70% reduction in boot time and will
> significantly reduce server downtime when using a large number of
> gigantic pages.

There were a few errors reported by kernel-bot if different config 
options were changed (CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP disabled, 
CONFIG_CMA enabled). I will fix these in the next revision if the 
general approach in the patches looks good to the community to start review.

Thanks,
Usama

> 
> Thanks,
> Usama
> 
> Usama Arif (4):
>    mm/hugetlb: Skip prep of tail pages when HVO is enabled
>    mm/memblock: Add hugepage_size member to struct memblock_region
>    mm/hugetlb_vmemmap: Use nid of the head page to reallocate it
>    mm/memblock: Skip initialization of struct pages freed later by HVO
> 
>   arch/arm64/mm/kasan_init.c                   |  2 +-
>   arch/powerpc/platforms/pasemi/iommu.c        |  2 +-
>   arch/powerpc/platforms/pseries/setup.c       |  4 +-
>   arch/powerpc/sysdev/dart_iommu.c             |  2 +-
>   include/linux/memblock.h                     |  8 +-
>   mm/cma.c                                     |  4 +-
>   mm/hugetlb.c                                 | 36 +++++---
>   mm/hugetlb_vmemmap.c                         |  6 +-
>   mm/hugetlb_vmemmap.h                         |  4 +
>   mm/memblock.c                                | 87 +++++++++++++-------
>   mm/mm_init.c                                 |  2 +-
>   mm/sparse-vmemmap.c                          |  2 +-
>   tools/testing/memblock/tests/alloc_nid_api.c |  2 +-
>   13 files changed, 106 insertions(+), 55 deletions(-)
>