On Thu, Jun 17, 2021 at 06:26:26PM +0900, Naoya Horiguchi wrote: > From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> > > Recent changes by patch "mm/page_alloc: allow high-order pages to be > stored on the per-cpu lists" makes kernels determine whether to use pcp > by pcp_allowed_order(), which breaks soft-offline for hugetlb pages. > > Soft-offline dissolves a migration source page, then removes it from > buddy free list, so it's assumed that any subpage of the soft-offlined > hugepage are recognized as a buddy page just after returning from > dissolve_free_huge_page(). pcp_allowed_order() returns true for > hugetlb, so this assumption is no longer true. > > So disable pcp during dissolve_free_huge_page() and > take_page_off_buddy() to prevent soft-offlined hugepages from linking to > pcp lists. Soft-offline should not be common events so the impact on > performance should be minimal. And I think that the optimization of > Mel's patch could benefit to hugetlb so zone_pcp_disable() is called > only in hwpoison context. > > Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> I think this is ok, it'll remove a page that is to be poisoned from the PCP lists and put them back in the page allocator. It's a heavy but rare operation and identifying what PCP list a free page is on would be tricky so Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> The alternative I guess would be specical casing update_and_free_page to bypass the PCP but it'd be clumsy from an API point of view and I don't think it's worth the effort. -- Mel Gorman SUSE Labs
