Message-ID: <20210205085940.GD13848@linux>
Date:   Fri, 5 Feb 2021 09:59:40 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     corbet@....net, mike.kravetz@...cle.com, tglx@...utronix.de,
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Subject: Re: [PATCH v14 0/8] Free some vmemmap pages of HugeTLB page

On Thu, Feb 04, 2021 at 11:50:35AM +0800, Muchun Song wrote:
> Changelog in v13 -> v14:
>   - Refuse to free the HugeTLB page when the system is under memory pressure.
>   - Use GFP_ATOMIC to allocate vmemmap pages instead of GFP_KERNEL.
>   - Rebase to linux-next 20210202.
>   - Fix and add some comments for vmemmap_remap_free().

What has happened to [1] ? AFAIK we still need it, right?
If not, could you explain why?

[1] https://patchwork.kernel.org/project/linux-mm/patch/20210117151053.24600-7-songmuchun@bytedance.com/

> 
>   Thanks to Oscar, Mike, David H and David R's suggestions and review.
> 
> Changelog in v12 -> v13:
>   - Remove VM_WARN_ON_PAGE macro.
>   - Add more comments in vmemmap_pte_range() and vmemmap_remap_free().
> 
>   Thanks to Oscar and Mike's suggestions and review.
> 
> Changelog in v11 -> v12:
>   - Move VM_WARN_ON_PAGE to a separate patch.
>   - Call __free_hugepage() with hugetlb_lock (See patch #5.) to serialize
>     with dissolve_free_huge_page(). It is to prepare for patch #9.
>   - Introduce PageHugeInflight. See patch #9.
> 
> Changelog in v10 -> v11:
>   - Fix compiler error when !CONFIG_HUGETLB_PAGE_FREE_VMEMMAP.
>   - Rework some comments and commit changes.
>   - Rework vmemmap_remap_free() to 3 parameters.
> 
>   Thanks to Oscar and Mike's suggestions and review.
> 
> Changelog in v9 -> v10:
>   - Fix a bug in patch #11. Thanks to Oscar for pointing that out.
>   - Rework some commit log or comments. Thanks Mike and Oscar for the suggestions.
>   - Drop VMEMMAP_TAIL_PAGE_REUSE in the patch #3.
> 
>   Thank you very much Mike and Oscar for reviewing the code.
> 
> Changelog in v8 -> v9:
>   - Rework some code. Very thanks to Oscar.
>   - Put all the non-hugetlb vmemmap functions under sparsemem-vmemmap.c.
> 
> Changelog in v7 -> v8:
>   - Adjust the order of patches.
> 
>   Very thanks to David and Oscar. Your suggestions are very valuable.
> 
> Changelog in v6 -> v7:
>   - Rebase to linux-next 20201130
>   - Do not use basepage mapping for vmemmap when this feature is disabled.
>   - Rework some patchs.
>     [PATCH v6 08/16] mm/hugetlb: Free the vmemmap pages associated with each hugetlb page
>     [PATCH v6 10/16] mm/hugetlb: Allocate the vmemmap pages associated with each hugetlb page
> 
>   Thanks to Oscar and Barry.
> 
> Changelog in v5 -> v6:
>   - Disable PMD/huge page mapping of vmemmap if this feature was enabled.
>   - Simplify the first version code.
> 
> Changelog in v4 -> v5:
>   - Rework somme comments and code in the [PATCH v4 04/21] and [PATCH v4 05/21].
> 
>   Thanks to Mike and Oscar's suggestions.
> 
> Changelog in v3 -> v4:
>   - Move all the vmemmap functions to hugetlb_vmemmap.c.
>   - Make the CONFIG_HUGETLB_PAGE_FREE_VMEMMAP default to y, if we want to
>     disable this feature, we should disable it by a boot/kernel command line.
>   - Remove vmemmap_pgtable_{init, deposit, withdraw}() helper functions.
>   - Initialize page table lock for vmemmap through core_initcall mechanism.
> 
>   Thanks for Mike and Oscar's suggestions.
> 
> Changelog in v2 -> v3:
>   - Rename some helps function name. Thanks Mike.
>   - Rework some code. Thanks Mike and Oscar.
>   - Remap the tail vmemmap page with PAGE_KERNEL_RO instead of PAGE_KERNEL.
>     Thanks Matthew.
>   - Add some overhead analysis in the cover letter.
>   - Use vmemap pmd table lock instead of a hugetlb specific global lock.
> 
> Changelog in v1 -> v2:
>   - Fix do not call dissolve_compound_page in alloc_huge_page_vmemmap().
>   - Fix some typo and code style problems.
>   - Remove unused handle_vmemmap_fault().
>   - Merge some commits to one commit suggested by Mike.
> 
> Muchun Song (8):
>   mm: memory_hotplug: factor out bootmem core functions to
>     bootmem_info.c
>   mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP
>   mm: hugetlb: free the vmemmap pages associated with each HugeTLB page
>   mm: hugetlb: alloc the vmemmap pages associated with each HugeTLB page
>   mm: hugetlb: add a kernel parameter hugetlb_free_vmemmap
>   mm: hugetlb: introduce nr_free_vmemmap_pages in the struct hstate
>   mm: hugetlb: gather discrete indexes of tail page
>   mm: hugetlb: optimize the code with the help of the compiler
> 
>  Documentation/admin-guide/kernel-parameters.txt |  14 ++
>  Documentation/admin-guide/mm/hugetlbpage.rst    |   3 +
>  arch/x86/mm/init_64.c                           |  13 +-
>  fs/Kconfig                                      |   6 +
>  include/linux/bootmem_info.h                    |  65 +++++
>  include/linux/hugetlb.h                         |  43 +++-
>  include/linux/hugetlb_cgroup.h                  |  19 +-
>  include/linux/memory_hotplug.h                  |  27 --
>  include/linux/mm.h                              |   5 +
>  mm/Makefile                                     |   2 +
>  mm/bootmem_info.c                               | 124 ++++++++++
>  mm/hugetlb.c                                    |  23 +-
>  mm/hugetlb_vmemmap.c                            | 314 ++++++++++++++++++++++++
>  mm/hugetlb_vmemmap.h                            |  33 +++
>  mm/memory_hotplug.c                             | 116 ---------
>  mm/sparse-vmemmap.c                             | 280 +++++++++++++++++++++
>  mm/sparse.c                                     |   1 +
>  17 files changed, 930 insertions(+), 158 deletions(-)
>  create mode 100644 include/linux/bootmem_info.h
>  create mode 100644 mm/bootmem_info.c
>  create mode 100644 mm/hugetlb_vmemmap.c
>  create mode 100644 mm/hugetlb_vmemmap.h
> 
> -- 
> 2.11.0
> 
> 

-- 
Oscar Salvador
SUSE L3

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