linux-kernel - Re: [RFC PATCH] page_ext: create page extension for all memblock memory regions

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Date:   Tue, 10 May 2022 09:00:12 +0900
From:   Jaewon Kim <jaewon31.kim@...il.com>
To:     Jaewon Kim <jaewon31.kim@...sung.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] page_ext: create page extension for all memblock
 memory regions

let me add Joonsoo Kim

2022년 5월 9일 (월) 오후 4:39, Jaewon Kim <jaewon31.kim@...sung.com>님이 작성:
>
> The page extension can be prepared for each section. But if the first
> page is not valid, the page extension for the section was not
> initialized though there were many other valid pages within the section.
>
> To support the page extension for all sections, refer to memblock memory
> regions. If the page is valid use the nid from pfn_to_nid, otherwise use
> the previous nid.
>
> Also this pagech changed log to include total sections and a section
> size.
>
> i.e.
> allocated 100663296 bytes of page_ext for 64 sections (1 section : 0x8000000)
>
> Signed-off-by: Jaewon Kim <jaewon31.kim@...sung.com>
> ---
>  mm/page_ext.c | 42 ++++++++++++++++++++++--------------------
>  1 file changed, 22 insertions(+), 20 deletions(-)
>
> diff --git a/mm/page_ext.c b/mm/page_ext.c
> index 2e66d934d63f..506d58b36a1d 100644
> --- a/mm/page_ext.c
> +++ b/mm/page_ext.c
> @@ -381,41 +381,43 @@ static int __meminit page_ext_callback(struct notifier_block *self,
>  void __init page_ext_init(void)
>  {
>         unsigned long pfn;
> -       int nid;
> +       int nid = 0;
> +       struct memblock_region *rgn;
> +       int nr_section = 0;
> +       unsigned long next_section_pfn = 0;
>
>         if (!invoke_need_callbacks())
>                 return;
>
> -       for_each_node_state(nid, N_MEMORY) {
> +       /*
> +        * iterate each memblock memory region and do not skip a section having
> +        * !pfn_valid(pfn)
> +        */
> +       for_each_mem_region(rgn) {
>                 unsigned long start_pfn, end_pfn;
>
> -               start_pfn = node_start_pfn(nid);
> -               end_pfn = node_end_pfn(nid);
> -               /*
> -                * start_pfn and end_pfn may not be aligned to SECTION and the
> -                * page->flags of out of node pages are not initialized.  So we
> -                * scan [start_pfn, the biggest section's pfn < end_pfn) here.
> -                */
> +               start_pfn = (unsigned long)(rgn->base >> PAGE_SHIFT);
> +               end_pfn = start_pfn + (unsigned long)(rgn->size >> PAGE_SHIFT);
> +
> +               if (start_pfn < next_section_pfn)
> +                       start_pfn = next_section_pfn;
> +
>                 for (pfn = start_pfn; pfn < end_pfn;
>                         pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
>
> -                       if (!pfn_valid(pfn))
> -                               continue;
> -                       /*
> -                        * Nodes's pfns can be overlapping.
> -                        * We know some arch can have a nodes layout such as
> -                        * -------------pfn-------------->
> -                        * N0 | N1 | N2 | N0 | N1 | N2|....
> -                        */
> -                       if (pfn_to_nid(pfn) != nid)
> -                               continue;
> +                       if (pfn_valid(pfn))
> +                               nid = pfn_to_nid(pfn);
> +                       nr_section++;
>                         if (init_section_page_ext(pfn, nid))
>                                 goto oom;
>                         cond_resched();
>                 }
> +               next_section_pfn = pfn;
>         }
> +
>         hotplug_memory_notifier(page_ext_callback, 0);
> -       pr_info("allocated %ld bytes of page_ext\n", total_usage);
> +       pr_info("allocated %ld bytes of page_ext for %d sections (1 section : 0x%x)\n",
> +               total_usage, nr_section, (1 << SECTION_SIZE_BITS));
>         invoke_init_callbacks();
>         return;
>
> --
> 2.17.1
>