From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-61.mta0.migadu.com [91.218.175.61]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F029E40926C for ; Mon, 24 Aug 2026 11:10:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.61 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787569809; cv=none; b=V2ETkg7nxiT5+kYRfl4ZWZCwop4GOiAWl4SSZw7ZyvZQ3DHnRFII3A+6YF0+eCv96xumYku5d7DSYZpSvlYuweZUUw/zg6nnrLgS2MSfktJZRIH2GduPbXc5lR56xe2JoDUQzoITOjms3YJFWhDbkBYqqS5dLpbJ/Qhc+clV9Y8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787569809; c=relaxed/simple; bh=MLoHlZQykALuphN6lnBx1ivPtGHUFJ0fv7fJkVRd95E=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pxP/Fn0iDQxPauT0SbQUMi4GA36hB9OFDEL/WyzChInVLlcIyuT4LZhfJn1sxCvXbU0zW1wQ2A9INicofoYwjflMvLzdW2dHj8OEhoSJdzjYVwVIpcuOfsuff+PflqiYkB+dKt48sHS/Xnri3kREeWk7yTZ4pC3b9sYZumepXJc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=EzyOSCUQ; arc=none smtp.client-ip=91.218.175.61 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="EzyOSCUQ" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=MLoHlZQykALuphN6lnBx1ivPtGHUFJ0fv7fJkVRd95E=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1787569804; v=1; x=1788174604; b=EzyOSCUQpaFtXFd3pa/3J36wjPwKSd3ccFmd76ctK8rqjTQpID7ryHZeOvouhZK+wm3XZFAd MwLUTd5E4B1wGekW9ZMm7wini0WeJjBPNAb0CUFOpUi0bFZf6aJRsvy8G8KuAxKEHoR4LXYpav2 /eSwIdRb9JTllmuE0BhFH1LA= X-Envelope-To: linux-kernel@vger.kernel.org Received: from [10.67.158.60] (114.251.196.91) by smtp.migadu.com with ESMTPS id b9a820b2082c8157; Mon, 24 Aug 2026 11:09:54 +0000 X-Mizu-Trace-ID: b9a820b2082c8157 X-Migadu-Flow: FLOW_OUT Message-ID: Date: Mon, 24 Aug 2026 19:09:45 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 08/17] mm/sparse-vmemmap: support section-based vmemmap optimization To: Mike Rapoport Cc: Andrew Morton , Oscar Salvador , David Hildenbrand , Vlastimil Babka , Lorenzo Stoakes , Michal Hocko , David Laight , "Liam R . Howlett" , Suren Baghdasaryan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song References: <20260819095140.17252-1-songmuchun@bytedance.com> <20260819095140.17252-9-songmuchun@bytedance.com> <178756196750.3606540.8562704442052486227.b4-review@b4> Content-Language: en-US From: Muchun Song In-Reply-To: <178756196750.3606540.8562704442052486227.b4-review@b4> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2026/8/24 16:59, Mike Rapoport wrote: >> Teach sparse-vmemmap population code to use the compound page order >> when deciding whether a vmemmap page can be optimized. >> >> With this information, the common sparse-vmemmap population path can >> allocate or reuse shared tail vmemmap pages directly instead of relying >> on HugeTLB-specific handling. >> >> This centralizes vmemmap optimization logic in the sparse-vmemmap code, >> based on section metadata, and prepares for sharing the same mechanism >> across different users of vmemmap optimization, including HugeTLB and >> DAX. >> >> Signed-off-by: Muchun Song >> >> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c >> index b770fe2428fd..737d50bdd3ef 100644 >> --- a/mm/sparse-vmemmap.c >> +++ b/mm/sparse-vmemmap.c >> @@ -186,6 +186,11 @@ static __meminit struct page *vmemmap_get_tail(unsigned int order, struct zone * >> >> return tail; >> } >> +#else >> +static inline struct page *vmemmap_get_tail(unsigned int order, struct zone *zone) >> +{ >> + return NULL; >> +} >> #endif >> >> static pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node, >> @@ -193,12 +198,24 @@ static pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, in >> unsigned long ptpfn, unsigned long flags) >> { >> pte_t *pte = pte_offset_kernel(pmd, addr); >> + unsigned long pfn = page_to_pfn((struct page *)addr); >> + >> if (pte_none(ptep_get(pte))) { >> pte_t entry; >> - void *p; >> + >> + if (vmemmap_optimizable_pfn(pfn) && ptpfn == (unsigned long)-1) { >> + unsigned int order = pfn_to_section_order(pfn); >> + struct zone *zone = pfn_to_zone(pfn, node); >> + struct page *page = vmemmap_get_tail(order, zone); >> + >> + if (!page) >> + return NULL; >> + ptpfn = page_to_pfn(page); >> + } >> >> if (ptpfn == (unsigned long)-1) { >> - p = vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap); >> + void *p = vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap); >> + > What do you think about adding a helper function here, e.g something > like Better than mine. More clear. > > diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c > index 0aa0ab4f8b11..933b122f9937 100644 > --- a/mm/sparse-vmemmap.c > +++ b/mm/sparse-vmemmap.c > @@ -191,6 +191,23 @@ static inline struct page *vmemmap_get_tail(unsigned int order, struct zone *zon > } > #endif > > +static void * __meminit vmemmap_alloc_pte(unsigned long pfn, int node, > + struct vmem_altmap *altmap) > +{ > + unsigned int order = pfn_to_section_order(pfn); > + struct zone *zone = pfn_to_zone(pfn, node); > + struct page *page; > + > + if (!vmemmap_optimizable_pfn(pfn)) > + return vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap); > + > + page = vmemmap_get_tail(order, zone); > + if (!page) > + return NULL; > + > + return page_address(page); > +} > + > static pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node, > struct vmem_altmap *altmap, > unsigned long ptpfn, unsigned long flags) > @@ -201,19 +218,8 @@ static pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, in > if (pte_none(ptep_get(pte))) { > pte_t entry; > > - if (vmemmap_optimizable_pfn(pfn) && ptpfn == (unsigned long)-1) { > - unsigned int order = pfn_to_section_order(pfn); > - struct zone *zone = pfn_to_zone(pfn, node); > - struct page *page = vmemmap_get_tail(order, zone); > - > - if (!page) > - return NULL; > - ptpfn = page_to_pfn(page); > - } > - > if (ptpfn == (unsigned long)-1) { > - void *p = vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap); > - > + void *p = vmemmap_alloc_pte(pfn, node, altmap); > if (!p) > return NULL; > ptpfn = PHYS_PFN(__pa(p)); > >> if (!p) >> return NULL; >> ptpfn = PHYS_PFN(__pa(p)); >> @@ -217,7 +234,8 @@ static pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, in >> } >> entry = pfn_pte(ptpfn, PAGE_KERNEL); >> set_pte_at(&init_mm, addr, pte, entry); >> - } >> + } else if (WARN_ON_ONCE(vmemmap_optimizable_pfn(pfn))) >> + return NULL; >> return pte; >> } >> >> @@ -406,6 +424,9 @@ int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end, >> pmd_t *pmd; >> >> for (addr = start; addr < end; addr = next) { >> + unsigned long pfn = page_to_pfn((struct page *)addr); >> + const struct mem_section *ms = __pfn_to_section(pfn); >> + >> next = pmd_addr_end(addr, end); >> >> pgd = vmemmap_pgd_populate(addr, node); >> @@ -421,7 +442,7 @@ int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end, >> return -ENOMEM; >> >> pmd = pmd_offset(pud, addr); >> - if (pmd_none(pmdp_get(pmd))) { >> + if (pmd_none(pmdp_get(pmd)) && !section_vmemmap_optimizable(ms)) { >> void *p; >> >> p = vmemmap_alloc_block_buf(PMD_SIZE, node, altmap); >> @@ -439,8 +460,11 @@ int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end, >> */ >> return -ENOMEM; >> } >> - } else if (vmemmap_check_pmd(pmd, node, addr, next)) >> + } else if (vmemmap_check_pmd(pmd, node, addr, next)) { >> + if (WARN_ON_ONCE(section_vmemmap_optimizable(ms))) >> + return -EOPNOTSUPP; >> continue; >> + } >> if (vmemmap_populate_basepages(addr, next, node, altmap)) >> return -ENOMEM; >> } >> @@ -620,6 +644,33 @@ void __init sparse_init_subsection_map(void) >> sparse_init_subsection_map_range(start, end - start); >> } >> >> +int __meminit section_nr_vmemmap_pages(unsigned long pfn, unsigned long nr_pages, >> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap) >> +{ > Can we do all code movements in separate patches? Yes. > Maybe even move this to the previous patch and update the changelog to > say "move code around in preparation ..." Make sense. Will do next version. Muchun, Thanks.