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SubjectRe: [PATCH v4 0/4] Make alloc_contig_range handle Hugetlb pages
On 2021-03-15 10:06, David Hildenbrand wrote:
> BTW, I stumbled yesterday over
>
> alloc_contig_pages()->pfn_range_valid_contig():
>
> if (page_count(page) > 0)
> rerurn false;
> if (PageHuge(page))
> return false;
>
> As used by memtrace and for gigantic pages. We can now
>
> a) Drop these check completely, as it's best-effort only and racy.
> alloc_contig_pages()/alloc_contig_range() will handle it properly.

I was preparing v5, and I wanted to be sure I understood you here.

Right you are that the in-use page check can be dropped, as those pages
can
be migrated away, and the Hugetlb page check can also be dropped since
isolate_migratepages_range is now capable of dealing with those kind of
pages.

> b) Similarly, check for gigantic pages and/or movability/migratability.

I lost you here.

isolate_or_dissolve_huge_page() already bails out on hugetlb-gigantic
pages.

Or do you mean to place an upfront check here? (hstate_is_gigantic())?


--
Oscar Salvador
SUSE L3

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