Messages in this thread | | | Date | Fri, 25 Aug 2023 11:51:34 +0800 | Subject | Re: [PATCH v2 1/8] mm: migrate: remove PageTransHuge check in numamigrate_isolate_page() | From | Kefeng Wang <> |
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On 2023/8/21 20:38, Matthew Wilcox wrote: > On Mon, Aug 21, 2023 at 07:56:17PM +0800, Kefeng Wang wrote: >> Since we begin to convert the numa migration code to use folio, which >> could let us to handle arbitrary sizes of folio, so drop assert that >> we only support PageTransHuge page(PMD size) when order > 0. > > Have you looked at the implementation of PageTransHuge()? Your > description doesn't match what the code does.
How about change to the following description,
The assert VM_BUG_ON_PAGE(order && !PageTransHuge(page), page) is not very usefull,
1) for a tail/base page, order = 0, for a head page, the order > 0 && PageTransHuge() is true 2) there is a PageCompound() check and only base page is handled in do_numa_page(), and do_huge_pmd_numa_page() only handle PMD-mapped THP 3) even though the page is a tail page, isolate_lru_page() will post a warning, and fail to isolate the page. 4) and if folio migrate is supported in the future, it is probable to migrate the entire folio if numa fault on a tail page
so just remove the check.
Thanks
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