From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-113.freemail.mail.aliyun.com (out30-113.freemail.mail.aliyun.com [115.124.30.113]) (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 8280426A0AB; Wed, 23 Apr 2025 07:30:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.113 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745393412; cv=none; b=ZeiAM0ZLNploGQupcki2heJkk3xr5m0gWYsacfIiznTZev88LEqpJSEc5qZ4QM+5h6dE5EDKrnMipEo03jHjQ2OaPyu5fwuBGmp5LXFgOjB7j2lguUvzeULmX1+TKnDOX9Z2S+6VW5K0dnK7NKasl0I3I5k2r5dERBlMXkKA6SA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745393412; c=relaxed/simple; bh=o+phP31kmrAYsA7kQQZnwNWQ6u/lBY83aHaSbMuUKkU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=SJCFhcBgL4VYef/Xw9sIVSYQJhR2LPlfhgOxuu/2+U4SW4/anTaa18f/tvPaYQOdeiEf/W25gt7LY6VCfp6cKNaVkBFY9wAe/tRTHycQvLk+l2hIrk6nFby31RkNdzV/eF9Iog0/fEOXvwhHfQP+fceQUZ98LpmtuE+VKL479go= ARC-Authentication-Results:i=1; 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Wed, 23 Apr 2025 15:30:03 +0800 Message-ID: Date: Wed, 23 Apr 2025 15:30:02 +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 05/12] khugepaged: generalize __collapse_huge_page_* for mTHP support To: Nico Pache , linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, david@redhat.com, baohua@kernel.org, ryan.roberts@arm.com, willy@infradead.org, peterx@redhat.com, ziy@nvidia.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kirill.shutemov@linux.intel.com, aarcange@redhat.com, raquini@redhat.com, dev.jain@arm.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 References: <20250417000238.74567-1-npache@redhat.com> <20250417000238.74567-6-npache@redhat.com> From: Baolin Wang In-Reply-To: <20250417000238.74567-6-npache@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025/4/17 08:02, Nico Pache wrote: > generalize the order of the __collapse_huge_page_* functions > to support future mTHP collapse. > > mTHP collapse can suffer from incosistant behavior, and memory waste > "creep". disable swapin and shared support for mTHP collapse. > > No functional changes in this patch. > > Co-developed-by: Dev Jain > Signed-off-by: Dev Jain > Signed-off-by: Nico Pache > --- > mm/khugepaged.c | 46 ++++++++++++++++++++++++++++------------------ > 1 file changed, 28 insertions(+), 18 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 883e9a46359f..5e9272ab82da 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -565,15 +565,17 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, > unsigned long address, > pte_t *pte, > struct collapse_control *cc, > - struct list_head *compound_pagelist) > + struct list_head *compound_pagelist, > + u8 order) > { > struct page *page = NULL; > struct folio *folio = NULL; > pte_t *_pte; > int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0; > bool writable = false; > + int scaled_none = khugepaged_max_ptes_none >> (HPAGE_PMD_ORDER - order); > > - for (_pte = pte; _pte < pte + HPAGE_PMD_NR; > + for (_pte = pte; _pte < pte + (1 << order); > _pte++, address += PAGE_SIZE) { > pte_t pteval = ptep_get(_pte); > if (pte_none(pteval) || (pte_present(pteval) && > @@ -581,7 +583,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, > ++none_or_zero; > if (!userfaultfd_armed(vma) && > (!cc->is_khugepaged || > - none_or_zero <= khugepaged_max_ptes_none)) { > + none_or_zero <= scaled_none)) { > continue; > } else { > result = SCAN_EXCEED_NONE_PTE; > @@ -609,8 +611,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, > /* See hpage_collapse_scan_pmd(). */ > if (folio_maybe_mapped_shared(folio)) { > ++shared; > - if (cc->is_khugepaged && > - shared > khugepaged_max_ptes_shared) { > + 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; > @@ -711,13 +713,14 @@ 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 list_head *compound_pagelist, > + u8 order) > { > struct folio *src, *tmp; > pte_t *_pte; > pte_t pteval; > > - for (_pte = pte; _pte < pte + HPAGE_PMD_NR; > + for (_pte = pte; _pte < pte + (1 << order); > _pte++, address += PAGE_SIZE) { > pteval = ptep_get(_pte); > if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { > @@ -764,7 +767,8 @@ 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) > + struct list_head *compound_pagelist, > + u8 order) > { > spinlock_t *pmd_ptl; > > @@ -781,7 +785,7 @@ 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 + (1 << order), compound_pagelist); > } > > /* > @@ -802,7 +806,7 @@ 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, > - struct list_head *compound_pagelist) > + struct list_head *compound_pagelist, u8 order) > { > unsigned int i; > int result = SCAN_SUCCEED; > @@ -810,7 +814,7 @@ static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio, > /* > * Copying pages' contents is subject to memory poison at any iteration. > */ > - for (i = 0; i < HPAGE_PMD_NR; i++) { > + for (i = 0; i < (1 << order); i++) { > pte_t pteval = ptep_get(pte + i); > struct page *page = folio_page(folio, i); > unsigned long src_addr = address + i * PAGE_SIZE; > @@ -829,10 +833,10 @@ 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); > + compound_pagelist, order); > else > __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma, > - compound_pagelist); > + compound_pagelist, order); > > return result; > } > @@ -1000,11 +1004,11 @@ static int check_pmd_still_valid(struct mm_struct *mm, > static int __collapse_huge_page_swapin(struct mm_struct *mm, > struct vm_area_struct *vma, > unsigned long haddr, pmd_t *pmd, > - int referenced) > + int referenced, u8 order) > { > int swapped_in = 0; > vm_fault_t ret = 0; > - unsigned long address, end = haddr + (HPAGE_PMD_NR * PAGE_SIZE); > + unsigned long address, end = haddr + (PAGE_SIZE << order); > int result; > pte_t *pte = NULL; > spinlock_t *ptl; > @@ -1035,6 +1039,12 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm, > if (!is_swap_pte(vmf.orig_pte)) > continue; > > + /* Dont swapin for mTHP collapse */ > + if (order != HPAGE_PMD_ORDER) { > + result = SCAN_EXCEED_SWAP_PTE; > + goto out; > + } IMO, this check should move into hpage_collapse_scan_pmd(), that means if we scan the swap ptes for mTHP collapse, then we can return 'SCAN_EXCEED_SWAP_PTE' to abort the collapse earlier. The logic is the same as how you handle the shared ptes for mTHP. > vmf.pte = pte; > vmf.ptl = ptl; > ret = do_swap_page(&vmf); > @@ -1154,7 +1164,7 @@ 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; > } > @@ -1201,7 +1211,7 @@ 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, > - &compound_pagelist); > + &compound_pagelist, HPAGE_PMD_ORDER); > spin_unlock(pte_ptl); > } else { > result = SCAN_PMD_NULL; > @@ -1231,7 +1241,7 @@ 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, > - &compound_pagelist); > + &compound_pagelist, HPAGE_PMD_ORDER); > pte_unmap(pte); > if (unlikely(result != SCAN_SUCCEED)) > goto out_up_write;