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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B249BFD4609 for ; Thu, 26 Feb 2026 03:24:12 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 22F636B008C; Wed, 25 Feb 2026 22:24:12 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1DA0E6B0092; Wed, 25 Feb 2026 22:24:12 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0BF816B0093; Wed, 25 Feb 2026 22:24:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id EE2D86B008C for ; Wed, 25 Feb 2026 22:24:11 -0500 (EST) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 8E8E71CA81 for ; Thu, 26 Feb 2026 03:24:11 +0000 (UTC) X-FDA: 84485164302.01.C31D4BB Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf22.hostedemail.com (Postfix) with ESMTP id B26E2C000A for ; Thu, 26 Feb 2026 03:24:09 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=TeBCEjxP; spf=pass (imf22.hostedemail.com: domain of npache@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=npache@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1772076249; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=HMaDPMdSo1wOJupzMtNfLzVgCQkuS95wkaCrSiv4DDs=; b=KheMAh4ALEtcMb3kUvl0Mp4MZm+vT/FYQP482rMI6ETNcy+y/aeom/a+zh63C/fXg6uXcS Opq4Gn6IaRkyLMtvK8TYK/xBEBFXCYWigQQQEYrrSeZAS87fnZl2Vl+rZG7O9ZG7qbvpMe yr9DmJ/tmyDZfmKOR4b7UazUVo3TQ98= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=TeBCEjxP; spf=pass (imf22.hostedemail.com: domain of npache@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=npache@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1772076249; a=rsa-sha256; cv=none; b=XVQqMsf7T/hJx5JhGczgbJTPex3cwVn8Qd1WGXNf2wlYiYaDGwb4BPg75pUqm0WFyU5suU pNzeV8yA9SfnzruljfKOXrTCMqfJXGGr7ocLGThMbOKoVo0yLuskPGKYwZyTbCBOIDolW1 TO6W9HZ8UvhgGnrM0cnKjvrplCnTPP0= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1772076247; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=HMaDPMdSo1wOJupzMtNfLzVgCQkuS95wkaCrSiv4DDs=; b=TeBCEjxPWmkA35KJEruR4eSZirWQ6KdOO50mc4JbBE3AX9kIT4CAD2rXib1WUftqYIEt30 dKvw0uBMP7D/jkPNWIfygNx8aKZduqmw86TqPfDJq556zFlUWwRYgTOSixhf+UHPK3uhJA hWPwvQiw6ipi0uFnuckDK1JhNnxCOLw= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-201-DcmLCHvzOm6sZTqh7hfWOA-1; Wed, 25 Feb 2026 22:24:05 -0500 X-MC-Unique: DcmLCHvzOm6sZTqh7hfWOA-1 X-Mimecast-MFC-AGG-ID: DcmLCHvzOm6sZTqh7hfWOA_1772076240 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 56D23195605F; Thu, 26 Feb 2026 03:23:59 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.64.173]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 3B8D83003D88; Thu, 26 Feb 2026 03:23:49 +0000 (UTC) From: Nico Pache To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Cc: aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@kernel.org, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jack@suse.cz, jackmanb@google.com, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, npache@redhat.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com Subject: [PATCH mm-unstable v15 03/13] mm/khugepaged: generalize __collapse_huge_page_* for mTHP support Date: Wed, 25 Feb 2026 20:23:47 -0700 Message-ID: <20260226032347.232939-1-npache@redhat.com> In-Reply-To: <20260226031741.230674-1-npache@redhat.com> References: <20260226031741.230674-1-npache@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: S1xynxlV8wY3ZW7QpuAqOGLhy_ggDMuvbcnMyq00h0w_1772076240 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Stat-Signature: p1jriehr9xu7acxudiq89qh6wiua7bdg X-Rspam-User: X-Rspamd-Queue-Id: B26E2C000A X-Rspamd-Server: rspam01 X-HE-Tag: 1772076249-279916 X-HE-Meta: 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 zMONXhgy 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: generalize the order of the __collapse_huge_page_* functions to support future mTHP collapse. mTHP collapse will not honor the khugepaged_max_ptes_shared or khugepaged_max_ptes_swap parameters, and will fail if it encounters a shared or swapped entry. No functional changes in this patch. Reviewed-by: Wei Yang Reviewed-by: Lance Yang Reviewed-by: Lorenzo Stoakes Reviewed-by: Baolin Wang Co-developed-by: Dev Jain Signed-off-by: Dev Jain Signed-off-by: Nico Pache --- mm/khugepaged.c | 73 +++++++++++++++++++++++++++++++------------------ 1 file changed, 47 insertions(+), 26 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index a9b645402b7f..ecdbbf6a01a6 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -535,7 +535,7 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte, static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma, unsigned long start_addr, pte_t *pte, struct collapse_control *cc, - struct list_head *compound_pagelist) + unsigned int order, struct list_head *compound_pagelist) { struct page *page = NULL; struct folio *folio = NULL; @@ -543,15 +543,17 @@ static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma, pte_t *_pte; int none_or_zero = 0, shared = 0, referenced = 0; enum scan_result result = SCAN_FAIL; + const unsigned long nr_pages = 1UL << order; + int max_ptes_none = khugepaged_max_ptes_none >> (HPAGE_PMD_ORDER - order); - for (_pte = pte; _pte < pte + HPAGE_PMD_NR; + for (_pte = pte; _pte < pte + nr_pages; _pte++, addr += PAGE_SIZE) { pte_t pteval = ptep_get(_pte); if (pte_none_or_zero(pteval)) { ++none_or_zero; if (!userfaultfd_armed(vma) && (!cc->is_khugepaged || - none_or_zero <= khugepaged_max_ptes_none)) { + none_or_zero <= max_ptes_none)) { continue; } else { result = SCAN_EXCEED_NONE_PTE; @@ -585,8 +587,14 @@ static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma, /* See collapse_scan_pmd(). */ if (folio_maybe_mapped_shared(folio)) { ++shared; - if (cc->is_khugepaged && - shared > khugepaged_max_ptes_shared) { + /* + * TODO: Support shared pages without leading to further + * mTHP collapses. Currently bringing in new pages via + * shared may cause a future higher order collapse on a + * rescan of the same range. + */ + if (!is_pmd_order(order) || (cc->is_khugepaged && + shared > khugepaged_max_ptes_shared)) { result = SCAN_EXCEED_SHARED_PTE; count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); goto out; @@ -679,18 +687,18 @@ static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma, } static void __collapse_huge_page_copy_succeeded(pte_t *pte, - struct vm_area_struct *vma, - unsigned long address, - spinlock_t *ptl, - struct list_head *compound_pagelist) + struct vm_area_struct *vma, unsigned long address, + spinlock_t *ptl, unsigned int order, + struct list_head *compound_pagelist) { - unsigned long end = address + HPAGE_PMD_SIZE; + unsigned long end = address + (PAGE_SIZE << order); struct folio *src, *tmp; pte_t pteval; pte_t *_pte; unsigned int nr_ptes; + const unsigned long nr_pages = 1UL << order; - for (_pte = pte; _pte < pte + HPAGE_PMD_NR; _pte += nr_ptes, + for (_pte = pte; _pte < pte + nr_pages; _pte += nr_ptes, address += nr_ptes * PAGE_SIZE) { nr_ptes = 1; pteval = ptep_get(_pte); @@ -743,13 +751,11 @@ static void __collapse_huge_page_copy_succeeded(pte_t *pte, } static void __collapse_huge_page_copy_failed(pte_t *pte, - pmd_t *pmd, - pmd_t orig_pmd, - struct vm_area_struct *vma, - struct list_head *compound_pagelist) + pmd_t *pmd, pmd_t orig_pmd, struct vm_area_struct *vma, + unsigned int order, struct list_head *compound_pagelist) { spinlock_t *pmd_ptl; - + const unsigned long nr_pages = 1UL << order; /* * Re-establish the PMD to point to the original page table * entry. Restoring PMD needs to be done prior to releasing @@ -763,7 +769,7 @@ static void __collapse_huge_page_copy_failed(pte_t *pte, * Release both raw and compound pages isolated * in __collapse_huge_page_isolate. */ - release_pte_pages(pte, pte + HPAGE_PMD_NR, compound_pagelist); + release_pte_pages(pte, pte + nr_pages, compound_pagelist); } /* @@ -783,16 +789,16 @@ static void __collapse_huge_page_copy_failed(pte_t *pte, */ static enum scan_result __collapse_huge_page_copy(pte_t *pte, struct folio *folio, pmd_t *pmd, pmd_t orig_pmd, struct vm_area_struct *vma, - unsigned long address, spinlock_t *ptl, + unsigned long address, spinlock_t *ptl, unsigned int order, struct list_head *compound_pagelist) { unsigned int i; enum scan_result result = SCAN_SUCCEED; - + const unsigned long nr_pages = 1UL << order; /* * Copying pages' contents is subject to memory poison at any iteration. */ - for (i = 0; i < HPAGE_PMD_NR; i++) { + for (i = 0; i < nr_pages; i++) { pte_t pteval = ptep_get(pte + i); struct page *page = folio_page(folio, i); unsigned long src_addr = address + i * PAGE_SIZE; @@ -811,10 +817,10 @@ static enum scan_result __collapse_huge_page_copy(pte_t *pte, struct folio *foli if (likely(result == SCAN_SUCCEED)) __collapse_huge_page_copy_succeeded(pte, vma, address, ptl, - compound_pagelist); + order, compound_pagelist); else __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma, - compound_pagelist); + order, compound_pagelist); return result; } @@ -985,12 +991,12 @@ static enum scan_result check_pmd_still_valid(struct mm_struct *mm, * Returns result: if not SCAN_SUCCEED, mmap_lock has been released. */ static enum scan_result __collapse_huge_page_swapin(struct mm_struct *mm, - struct vm_area_struct *vma, unsigned long start_addr, pmd_t *pmd, - int referenced) + struct vm_area_struct *vma, unsigned long start_addr, + pmd_t *pmd, int referenced, unsigned int order) { int swapped_in = 0; vm_fault_t ret = 0; - unsigned long addr, end = start_addr + (HPAGE_PMD_NR * PAGE_SIZE); + unsigned long addr, end = start_addr + (PAGE_SIZE << order); enum scan_result result; pte_t *pte = NULL; spinlock_t *ptl; @@ -1022,6 +1028,19 @@ static enum scan_result __collapse_huge_page_swapin(struct mm_struct *mm, pte_present(vmf.orig_pte)) continue; + /* + * TODO: Support swapin without leading to further mTHP + * collapses. Currently bringing in new pages via swapin may + * cause a future higher order collapse on a rescan of the same + * range. + */ + if (!is_pmd_order(order)) { + pte_unmap(pte); + mmap_read_unlock(mm); + result = SCAN_EXCEED_SWAP_PTE; + goto out; + } + vmf.pte = pte; vmf.ptl = ptl; ret = do_swap_page(&vmf); @@ -1141,7 +1160,7 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long a * that case. Continuing to collapse causes inconsistency. */ result = __collapse_huge_page_swapin(mm, vma, address, pmd, - referenced); + referenced, HPAGE_PMD_ORDER); if (result != SCAN_SUCCEED) goto out_nolock; } @@ -1189,6 +1208,7 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long a pte = pte_offset_map_lock(mm, &_pmd, address, &pte_ptl); if (pte) { result = __collapse_huge_page_isolate(vma, address, pte, cc, + HPAGE_PMD_ORDER, &compound_pagelist); spin_unlock(pte_ptl); } else { @@ -1219,6 +1239,7 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long a result = __collapse_huge_page_copy(pte, folio, pmd, _pmd, vma, address, pte_ptl, + HPAGE_PMD_ORDER, &compound_pagelist); pte_unmap(pte); if (unlikely(result != SCAN_SUCCEED)) -- 2.53.0