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SubjectRe: [PATCH 2/2] mm: compaction: skip the memory hole rapidly when isolating free pages
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On 07.07.23 10:51, Baolin Wang wrote:
> On my machine with below memory layout, and I can see it will take more
> time to skip the larger memory hole (range: 0x100000000 - 0x1800000000)
> when isolating free pages. So adding a new helper to skip the memory
> hole rapidly, which can reduce the time consumed from about 70us to less
> than 1us.

Can you clarify how this relates to the previous commit and mention that
commit?

>
> [ 0.000000] Zone ranges:
> [ 0.000000] DMA [mem 0x0000000040000000-0x00000000ffffffff]
> [ 0.000000] DMA32 empty
> [ 0.000000] Normal [mem 0x0000000100000000-0x0000001fa7ffffff]
> [ 0.000000] Movable zone start for each node
> [ 0.000000] Early memory node ranges
> [ 0.000000] node 0: [mem 0x0000000040000000-0x0000000fffffffff]
> [ 0.000000] node 0: [mem 0x0000001800000000-0x0000001fa3c7ffff]
> [ 0.000000] node 0: [mem 0x0000001fa3c80000-0x0000001fa3ffffff]
> [ 0.000000] node 0: [mem 0x0000001fa4000000-0x0000001fa402ffff]
> [ 0.000000] node 0: [mem 0x0000001fa4030000-0x0000001fa40effff]
> [ 0.000000] node 0: [mem 0x0000001fa40f0000-0x0000001fa73cffff]
> [ 0.000000] node 0: [mem 0x0000001fa73d0000-0x0000001fa745ffff]
> [ 0.000000] node 0: [mem 0x0000001fa7460000-0x0000001fa746ffff]
> [ 0.000000] node 0: [mem 0x0000001fa7470000-0x0000001fa758ffff]
> [ 0.000000] node 0: [mem 0x0000001fa7590000-0x0000001fa7ffffff]
>
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
> mm/compaction.c | 30 +++++++++++++++++++++++++++++-
> 1 file changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 43358efdbdc2..9641e2131901 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -249,11 +249,31 @@ static unsigned long skip_offline_sections(unsigned long start_pfn)
>
> return 0;
> }
> +
> +static unsigned long skip_offline_sections_reverse(unsigned long start_pfn)
> +{
> + unsigned long start_nr = pfn_to_section_nr(start_pfn);
> +
> + if (!start_nr || online_section_nr(start_nr))
> + return 0;
> +
> + while (start_nr-- > 0) {
> + if (online_section_nr(start_nr))
> + return section_nr_to_pfn(start_nr) + PAGES_PER_SECTION - 1;
> + }
> +
> + return 0;
> +}
> #else
> static unsigned long skip_offline_sections(unsigned long start_pfn)
> {
> return 0;
> }
> +
> +static unsigned long skip_offline_sections_reverse(unsigned long start_pfn)
> +{
> + return 0;
> +}
> #endif
>
> /*
> @@ -1668,8 +1688,16 @@ static void isolate_freepages(struct compact_control *cc)
>
> page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
> zone);
> - if (!page)
> + if (!page) {
> + unsigned long next_pfn;
> +
> + next_pfn = skip_offline_sections_reverse(block_start_pfn);
> + if (next_pfn)
> + block_start_pfn = max(pageblock_start_pfn(next_pfn),
> + low_pfn);
> +
> continue;
> + }
>
> /* Check the block is suitable for migration */
> if (!suitable_migration_target(cc, page))


LGTM

Acked-by: David Hildenbrand <david@redhat.com>

--
Cheers,

David / dhildenb

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