From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 92BB237AA65 for ; Mon, 31 Aug 2026 23:46:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788219970; cv=none; b=ZwnfFm8RHaZRspeJv54XHo/wnK0kZQNAMDei+OOigJUOYCaez5KAb5NrAzZjTR68sZ+juIB6fv3rdVIy03iOGshK3MJ3XbRarxoeO12GjBBE1ACS/+esRLu+HSMwG2xcnQH9FZK9xP9eBoZ7vKqAYGawUJW8q/MNYTPH6Q+OPBI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788219970; c=relaxed/simple; bh=bmmYXQ838xE+ui0K+t0SltpUuVivPYiQpc82mXt+1uo=; h=Date:To:From:Subject:Message-Id; b=DPisyFp+UclModIcxeNue+uBwynX59D1wnWqCBji3kwHl6US2mtJe1a83T3QShKJlqMEs1c8K6+v67bhKNn51k0pEk/1e7k8iIupU6S81wji9AJ8tOsQoNxzk6H1PWWb1Ql3+7EvkhuHIbDONIpb02TAiuKl3UJykYwr4neAhZw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=hdj7TYQQ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="hdj7TYQQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1B37A1F00A3D; Mon, 31 Aug 2026 23:46:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1788219969; bh=UpQDDCtG99Kfa+UFkvYbmnbtH5upGzufv2JhhA9Q96Q=; h=Date:To:From:Subject; b=hdj7TYQQCKSMAkZ8/1xp0fZSdiVj4B+5DHnzXnOxyxN+FxEDVwcpDJs2JC1SgS4+z 1LaeDJRcMNwWH5NnhOfZJIP06M7a5A2Pv/+WG4mP7qO1HeVMtFFsPK/Jiz9yjLIP4R s1PZJut9SlZSzjR7QzsAt9k8FR3L9BBu9JKVJABM= Date: Mon, 31 Aug 2026 16:46:08 -0700 To: mm-commits@vger.kernel.org,rppt@kernel.org,muchun.song@linux.dev,mingo@redhat.com,kees@kernel.org,david@kernel.org,dave.hansen@linux.intel.com,bp@alien8.de,balbirs@nvidia.com,arnd@arndb.de,apopple@nvidia.com,lizhe.67@bytedance.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-extend-the-template-fast-path-to-zone-device-compound-tails.patch added to mm-new branch Message-Id: <20260831234609.1B37A1F00A3D@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm: extend the template fast path to zone-device compound tails has been added to the -mm mm-new branch. Its filename is mm-extend-the-template-fast-path-to-zone-device-compound-tails.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-extend-the-template-fast-path-to-zone-device-compound-tails.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next If a few days of testing in mm-new is successful, the patch will me moved into mm.git's mm-unstable branch, which is included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: "Li Zhe" Subject: mm: extend the template fast path to zone-device compound tails Date: Mon, 31 Aug 2026 19:16:35 +0800 The template fast path from the previous patch only accelerates head pages. Compound tails in memmap_init_compound() still go through the normal initialization path one by one. Build separate head and tail templates and reuse one prepared tail template across the tail pages in a compound range. Head pages preserve the existing refcount policy, while compound tails always start with a refcount of 0 after prep_compound_tail(). This extends the template-copy fast path to pfns_per_compound > 1. Tail-page PFN-dependent fields are refreshed in the reusable tail template before each copy. Do not keep a separate non-template fallback for compound tails either. These pages are still under memmap initialization, and the initialization-time refcount updates are not part of the observable lifetime of pages handed out later. The impact is controlled for the same reason as for head pages. The first tail page still seeds the reusable tail template through the normal tail initialization sequence, and the copied tail pages have the same final initialized state except for the PFN-dependent fields refreshed before each copy. Tested in a VM with a 100 GB devdax namespace (align=2097152) on Intel Ice Lake server. This test exercises the dax_pmem rebind path and measures memmap initialization latency. Test procedure: Unbind and rebind the dax_pmem driver 30 times, collect memmap initialization time from the pr_debug() output of memmap_init_zone_device(). Base(v7.3-rc1): Average of rebinds for dax_pmem driver: 191.20 ms With this patch and its prerequisites applied: Average of rebinds for dax_pmem driver: 176.87 ms This reduces the average memmap initialization time measured during rebind from 191.20 ms to 176.87 ms, or about 7.5%. Link: https://lore.kernel.org/20260831111638.76012-5-lizhe.67@bytedance.com Signed-off-by: Li Zhe Cc: Alistair Popple Cc: Arnd Bergmann Cc: Balbir Singh Cc: "Borislav Petkov (AMD)" Cc: Dave Hansen Cc: David Hildenbrand (Arm) Cc: Ingo Molnar Cc: Kees Cook Cc: Mike Rapoport (Microsoft) Cc: Muchun Song Signed-off-by: Andrew Morton --- mm/mm_init.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) --- a/mm/mm_init.c~mm-extend-the-template-fast-path-to-zone-device-compound-tails +++ a/mm/mm_init.c @@ -1072,6 +1072,8 @@ static void __ref memmap_init_compound(s { unsigned long pfn, end_pfn = head_pfn + nr_pages; unsigned int order = pgmap->vmemmap_shift; + struct page template; + struct page *page; /* * We have to initialize the pages, including setting up page links. @@ -1080,13 +1082,23 @@ static void __ref memmap_init_compound(s * the pages in the same go. */ __SetPageHead(head); - for (pfn = head_pfn + 1; pfn < end_pfn; pfn++) { - struct page *page = pfn_to_page(pfn); - __init_zone_device_page(page, pfn, zone_idx, nid, pgmap); - prep_compound_tail(page, head, order); - set_page_count(page, 0); - } + /* + * All tails of the same compound page share the state established by + * prep_compound_tail(). Reuse one tail template for the whole range and + * refresh only the PFN-dependent fields in that template before each copy. + */ + pfn = head_pfn + 1; + page = pfn_to_page(pfn); + __init_zone_device_page(page, pfn, zone_idx, nid, pgmap); + prep_compound_tail(page, head, order); + set_page_count(page, 0); + memcpy(&template, page, sizeof(*page)); + + /* Initialize the remaining tail pages from template. */ + for (pfn = head_pfn + 2; pfn < end_pfn; pfn++) + zone_device_page_init_from_template(pfn_to_page(pfn), pfn, + &template); prep_compound_head(head, order); } _ Patches currently in -mm which might be from lizhe.67@bytedance.com are mm-fix-stale-zone_device-refcount-comment.patch mm-add-a-set_page_section_from_pfn-helper.patch mm-add-a-template-based-fast-path-for-zone-device-page-init.patch mm-extend-the-template-fast-path-to-zone-device-compound-tails.patch string-introduce-memcpy_nontemporal.patch mm-use-memcpy_nontemporal-in-zone-device-template-copies.patch x86-string-extend-memcpy_flushcache-fixed-size-fastpaths.patch