From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2E05AF53D78 for ; Mon, 16 Mar 2026 17:02:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=3HUgCrkEW0pocbKYXLc4Jk+u5KcjTBdkxib9as1G+bM=; b=SMbTV3x8JanOnH NpucyhM9BLU1EonLb++gCjdBn3zEMxtS/AN/EkjrcIYT2UsPKQV8rI6wYRwxuRMz1NaD3irPiOOsX VoWPsqtOci2mzFL0aWYgrLxyrmwiNHVzLxDuSmuhOZ/Hv+bccUAAAEy0gH6feNSrJ0ZD/0AmOaUBl GOwuFH3zion8EUF/v/DWj7XU3csYyAKR9KR9j/eRG/NXu/tc35NfOX6a7qwrp0JfRMbMxIDnR0ere ZNmFlcKFJWjS61KSJLL/6g4fAZBZJMR+0cCxagvGGpE2uBi/oTByx+w3quU6Fm/k2KcRjmgUhcYxZ PtPvm3WEMBD7+L7i0nZA==; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On 2/27/26 20:42, Kiryl Shutsemau (Meta) wrote: > From: Kiryl Shutsemau > > HugeTLB Vmemmap Optimization (HVO) reduces memory usage by freeing most > vmemmap pages for huge pages and remapping the freed range to a single > page containing the struct page metadata. > > With the new mask-based compound_info encoding (for power-of-2 struct > page sizes), all tail pages of the same order are now identical > regardless of which compound page they belong to. This means the tail > pages can be truly shared without fake heads. > > Allocate a single page of initialized tail struct pages per zone > per order in the vmemmap_tails[] array in struct zone. All huge pages of > that order in the zone share this tail page, mapped read-only into their > vmemmap. The head page remains unique per huge page. > > Redefine MAX_FOLIO_ORDER using ilog2(). The define has to produce a > compile-constant as it is used to specify vmemmap_tail array size. > For some reason, compiler is not able to solve get_order() at > compile-time, but ilog2() works. > > Avoid PUD_ORDER to define MAX_FOLIO_ORDER as it adds dependency to > which generates hard-to-break include loop. > > This eliminates fake heads while maintaining the same memory savings, > and simplifies compound_head() by removing fake head detection. > > Signed-off-by: Kiryl Shutsemau > --- [...] > > +static struct zone *pfn_to_zone(unsigned nid, unsigned long pfn) I'd make it clearer that this some hugetlb helper, not just some page_zone(pfn_to_page()). Also, it's only really valid during boot, where we cannot have overlapping zones yet (hopefully IIRC). static struct zone *hugetlb_early_pfn_to_zone(unsigned nid, unsigned long pfn) or sth. like that (throwing in an __init). [...] > index c76122f22294..928e79c7549c 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -886,6 +886,15 @@ static inline void prep_compound_tail(struct page *tail, > set_page_private(tail, 0); > } > > +static inline void init_compound_tail(struct page *tail, > + const struct page *head, unsigned int order, struct zone *zone) > +{ In light of the refcount rework (lock/frozen bit), it might make sense to directly set the page count here to 0, so it's easier to spot and consider later. set_page_count(tail, 0) > + atomic_set(&tail->_mapcount, -1); > + set_page_node(tail, zone_to_nid(zone)); > + set_page_zone(tail, zone_idx(zone)); > + prep_compound_tail(tail, head, order); > +} > + Nothing else jumped at me Acked-by: David Hildenbrand (Arm) -- Cheers, David _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv