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 E3D63CCF9E0 for ; Mon, 27 Oct 2025 09:17:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 29F0D8002B; Mon, 27 Oct 2025 05:17:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 24F9C8000A; Mon, 27 Oct 2025 05:17:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 13E028002B; Mon, 27 Oct 2025 05:17:54 -0400 (EDT) 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 01CFE8000A for ; Mon, 27 Oct 2025 05:17:53 -0400 (EDT) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 9675EC0559 for ; Mon, 27 Oct 2025 09:17:53 +0000 (UTC) X-FDA: 84043342026.25.7BB00B0 Received: from out-172.mta0.migadu.com (out-172.mta0.migadu.com [91.218.175.172]) by imf20.hostedemail.com (Postfix) with ESMTP id C11391C0003 for ; Mon, 27 Oct 2025 09:17:51 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=a7VpjxJd; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf20.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.172 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1761556672; 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=dm/mUbcMAMZo9wS8DsBcQxN0CKzM7e2WXj+TwSYfMcs=; b=mdcwZO+2SUnOsSATR7JDAjPaptVNhtd7yuhp2JWNvdMWOa+3lqj5WLlLisrjdOCWshd5kc Nm8ogU0qEZ5/CrZJzyDf57I9nfyPDuE0kmmMV+XKw1YSdSA6qE7IcZA8/fGgU8yu4JtArZ JmXXnXkbHTUujxEwri9TOkzsvnckuH8= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1761556672; a=rsa-sha256; cv=none; b=0AJ7vtkMEJkAd0i9ZTcrOz+HbWcGhi4R8QKf/gGefqxYyg5cuxwR53w63YvtAhwcCpD8y7 CcQotFw4KPBz6G1i+VzpxUstsE2ZAz2ZbgB0M+tSnC0uPdWkFOywS6F/oj3UqruciXBHxC YALgBP46TIecXK0UxGdm4qEy9wE/3XY= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=a7VpjxJd; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf20.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.172 as permitted sender) smtp.mailfrom=lance.yang@linux.dev Message-ID: <703b22dc-0123-42ba-9984-074b9cda468c@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1761556668; 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=dm/mUbcMAMZo9wS8DsBcQxN0CKzM7e2WXj+TwSYfMcs=; b=a7VpjxJdsAE7IaId8HUK0fWulHLBBBlPdBgisXLI8HsC5jSpnqn0RWI3TOiFJ+HoLyFGKb fOsLV6/nyVa7CRopxslpJS2jE6iPH3Y7UVgkHeh1oxU5h/DTMIp9n83ksu3aSf5DB9BdIe AAPk02rr8BVzg6VEVgfCPY6Y71vljfo= Date: Mon, 27 Oct 2025 17:17:28 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v12 mm-new 05/15] khugepaged: generalize __collapse_huge_page_* for mTHP support Content-Language: en-US To: Nico Pache Cc: david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, baohua@kernel.org, willy@infradead.org, peterx@redhat.com, wangkefeng.wang@huawei.com, linux-mm@kvack.org, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kas@kernel.org, aarcange@redhat.com, raquini@redhat.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, surenb@google.com, zokeefe@google.com, hannes@cmpxchg.org, rientjes@google.com, mhocko@suse.com, rdunlap@infradead.org, hughd@google.com, richard.weiyang@gmail.com, vbabka@suse.cz, rppt@kernel.org, jannh@google.com, pfalcato@suse.de, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org References: <20251022183717.70829-1-npache@redhat.com> <20251022183717.70829-6-npache@redhat.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <20251022183717.70829-6-npache@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam01 X-Stat-Signature: p938d1rifih3kkgim9wegjsfa3toke6u X-Rspam-User: X-Rspamd-Queue-Id: C11391C0003 X-HE-Tag: 1761556671-470958 X-HE-Meta: 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 BKKFDgFt LbjV9yNB+o5yr/+QRscMbUCDkLzSnLc4XeAO6W1zRa5vVLgDG9t8Ize4FWXDcWZqfwV9plDu3uodN2mYiByYBMIOudx4I+ZIlXe8N2hmbqnlLKkWfyA66MRUl28cYSczsW80WIjViui9KhU/NyaSZK+0/UN3d7ChiL9QZSFn5VcGKogjdZs8f8NOa1Q/qIyjC4zK7/ytGiTH9l5ddKwp6pN6DfY1/0ekMsLrYIquymXi2gnoMUPgTyV6JXRhfB8jYqH4CAK+TdTmS29yu6WHhiv8MrBGIhl8yNOPdyA9Na5c86k5rhs1EfhFc2XG0Rab3Vvcsc96w+ExlBinIugiBCAssOVVi8NCP86G47GKx3unVLyMcMCbtDD8g5e3oM/GFZj6V0IEja2Fqwe7GRA30bQmlB+O5EHD4cQes5dWbnS1NhUasjltLBI3mtw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2025/10/23 02:37, Nico Pache wrote: > 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. Yeah, IMHO, it's the right call to avoid the complexity of potential "collapse creep" at this stage and get the core functionality right first ;) > > No functional changes in this patch. > > Reviewed-by: Baolin Wang > Acked-by: David Hildenbrand > Co-developed-by: Dev Jain > Signed-off-by: Dev Jain > Signed-off-by: Nico Pache > --- Cool! LGTM. Reviewed-by: Lance Yang > mm/khugepaged.c | 78 ++++++++++++++++++++++++++++++------------------- > 1 file changed, 48 insertions(+), 30 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 36ee659acfbb..4ccebf5dda97 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -537,25 +537,25 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte, > } > > static int __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 long start_addr, pte_t *pte, struct collapse_control *cc, > + unsigned int order, struct list_head *compound_pagelist) > { > struct page *page = NULL; > struct folio *folio = NULL; > unsigned long addr = start_addr; > pte_t *_pte; > int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0; > + 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; > @@ -583,8 +583,14 @@ static int __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 (order != HPAGE_PMD_ORDER || (cc->is_khugepaged && > + shared > khugepaged_max_ptes_shared)) { > result = SCAN_EXCEED_SHARED_PTE; > count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); > goto out; > @@ -677,18 +683,18 @@ static int __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); > @@ -741,13 +747,11 @@ 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 > @@ -761,7 +765,7 @@ 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); > } > > /* > @@ -781,16 +785,16 @@ static void __collapse_huge_page_copy_failed(pte_t *pte, > */ > static int __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; > int 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; > @@ -809,10 +813,10 @@ static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio, > > 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; > } > @@ -985,13 +989,12 @@ static int check_pmd_still_valid(struct mm_struct *mm, > * Returns result: if not SCAN_SUCCEED, mmap_lock has been released. > */ > static int __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); > int result; > pte_t *pte = NULL; > spinlock_t *ptl; > @@ -1022,6 +1025,19 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm, > if (!is_swap_pte(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 (order != HPAGE_PMD_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); > @@ -1142,7 +1158,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > * 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; > } > @@ -1190,6 +1206,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > 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 { > @@ -1220,6 +1237,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > > 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))