From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-119.freemail.mail.aliyun.com (out30-119.freemail.mail.aliyun.com [115.124.30.119]) (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 D8A4E502B1; Thu, 24 Apr 2025 12:21:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.119 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745497317; cv=none; b=HpKzsLjdE2e3epleNpjZqZF4TYnq1HIWLrY+1QxWEI3x7sP9SVPFSSgBRkTn0XVwKwFmTCOany8MMVyF+WSc7ZD/vxYb3BTjPYMPtN00kT+pL6YSlNaRcBiEYsPgOFf8QcKb1rT4mX4Nd0p3IXOugnq6Y3gJUX9M76HkawvpOy4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745497317; c=relaxed/simple; bh=M7139PzVyYycpaeFCqj8wuCKkvCagsdDr6j8nz7nMT0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KTLtcdhhMF4PVBHJc0WUKJyRbyJ4mRnW13Cs09L9mTyT7O4r76l+iybNepyVWOOXlN305FQ336+VnqWaZb4csCU7DrgkeAS5ob0GDOsGv/hUPLgf9VGcc+u6Z5Rhzu3rk96AfOGKX4GYdoV2z/Q4sTIzZ7Ji/3vhCmgjtGtuJT4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=ZI8b75Rw; arc=none smtp.client-ip=115.124.30.119 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="ZI8b75Rw" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1745497308; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=96rZkPR8RJnCqVOLwUnJiqjdHf3YOUV8iWh99OEjfFk=; b=ZI8b75RwNdn+zpP62lJ28pPSrjjlhRUs9Kq/1qLYBpnRlAwn4qHpuPMX6xHKYl7pmoslFw5Oi71UGLo8w+irKTjioB6w1Ko2XugtcCUhBqeTykh68neMIg5vnDjgK7W3vAK+b3NlkxnaT0Roktqp5nLKj+F5/2K/lQSENei3EL0= Received: from 192.168.1.7(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WXzOB6s_1745497303 cluster:ay36) by smtp.aliyun-inc.com; Thu, 24 Apr 2025 20:21:45 +0800 Message-ID: <3f52af67-489d-46b0-867f-202b59864692@linux.alibaba.com> Date: Thu, 24 Apr 2025 20:21:43 +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 07/12] khugepaged: add 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> <20250417000238.74567-8-npache@redhat.com> From: Baolin Wang In-Reply-To: <20250417000238.74567-8-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: > Introduce the ability for khugepaged to collapse to different mTHP sizes. > While scanning PMD ranges for potential collapse candidates, keep track > of pages in KHUGEPAGED_MIN_MTHP_ORDER chunks via a bitmap. Each bit > represents a utilized region of order KHUGEPAGED_MIN_MTHP_ORDER ptes. If > mTHPs are enabled we remove the restriction of max_ptes_none during the > scan phase so we dont bailout early and miss potential mTHP candidates. > > After the scan is complete we will perform binary recursion on the > bitmap to determine which mTHP size would be most efficient to collapse > to. max_ptes_none will be scaled by the attempted collapse order to > determine how full a THP must be to be eligible. > > If a mTHP collapse is attempted, but contains swapped out, or shared > pages, we dont perform the collapse. > > Signed-off-by: Nico Pache > --- > mm/khugepaged.c | 122 ++++++++++++++++++++++++++++++++++-------------- > 1 file changed, 88 insertions(+), 34 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 83230e9cdf3a..ece39fd71fe6 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1136,13 +1136,14 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > { > LIST_HEAD(compound_pagelist); > pmd_t *pmd, _pmd; > - pte_t *pte; > + pte_t *pte, mthp_pte; > pgtable_t pgtable; > struct folio *folio; > spinlock_t *pmd_ptl, *pte_ptl; > int result = SCAN_FAIL; > struct vm_area_struct *vma; > struct mmu_notifier_range range; > + unsigned long _address = address + offset * PAGE_SIZE; > > VM_BUG_ON(address & ~HPAGE_PMD_MASK); > > @@ -1158,12 +1159,13 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > *mmap_locked = false; > } > > - result = alloc_charge_folio(&folio, mm, cc, HPAGE_PMD_ORDER); > + result = alloc_charge_folio(&folio, mm, cc, order); > if (result != SCAN_SUCCEED) > goto out_nolock; > > mmap_read_lock(mm); > - result = hugepage_vma_revalidate(mm, address, true, &vma, cc, HPAGE_PMD_ORDER); > + *mmap_locked = true; > + result = hugepage_vma_revalidate(mm, address, true, &vma, cc, order); > if (result != SCAN_SUCCEED) { > mmap_read_unlock(mm); > goto out_nolock; > @@ -1181,13 +1183,14 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > * released when it fails. So we jump out_nolock directly in > * that case. Continuing to collapse causes inconsistency. > */ > - result = __collapse_huge_page_swapin(mm, vma, address, pmd, > - referenced, HPAGE_PMD_ORDER); > + result = __collapse_huge_page_swapin(mm, vma, _address, pmd, > + referenced, order); > if (result != SCAN_SUCCEED) > goto out_nolock; > } > > mmap_read_unlock(mm); > + *mmap_locked = false; > /* > * Prevent all access to pagetables with the exception of > * gup_fast later handled by the ptep_clear_flush and the VM > @@ -1197,7 +1200,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > * mmap_lock. > */ > mmap_write_lock(mm); > - result = hugepage_vma_revalidate(mm, address, true, &vma, cc, HPAGE_PMD_ORDER); > + result = hugepage_vma_revalidate(mm, address, true, &vma, cc, order); > if (result != SCAN_SUCCEED) > goto out_up_write; > /* check if the pmd is still valid */ > @@ -1208,11 +1211,12 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > vma_start_write(vma); > anon_vma_lock_write(vma->anon_vma); > > - mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, address, > - address + HPAGE_PMD_SIZE); > + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, _address, > + _address + (PAGE_SIZE << order)); > mmu_notifier_invalidate_range_start(&range); > > pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ > + > /* > * This removes any huge TLB entry from the CPU so we won't allow > * huge and small TLB entries for the same virtual address to > @@ -1226,10 +1230,10 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > mmu_notifier_invalidate_range_end(&range); > tlb_remove_table_sync_one(); > > - pte = pte_offset_map_lock(mm, &_pmd, address, &pte_ptl); > + pte = pte_offset_map_lock(mm, &_pmd, _address, &pte_ptl); > if (pte) { > - result = __collapse_huge_page_isolate(vma, address, pte, cc, > - &compound_pagelist, HPAGE_PMD_ORDER); > + result = __collapse_huge_page_isolate(vma, _address, pte, cc, > + &compound_pagelist, order); > spin_unlock(pte_ptl); > } else { > result = SCAN_PMD_NULL; > @@ -1258,8 +1262,8 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > anon_vma_unlock_write(vma->anon_vma); > > result = __collapse_huge_page_copy(pte, folio, pmd, _pmd, > - vma, address, pte_ptl, > - &compound_pagelist, HPAGE_PMD_ORDER); > + vma, _address, pte_ptl, > + &compound_pagelist, order); > pte_unmap(pte); pte is unmapped here, but... > if (unlikely(result != SCAN_SUCCEED)) > goto out_up_write; > @@ -1270,20 +1274,35 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > * write. > */ > __folio_mark_uptodate(folio); > - pgtable = pmd_pgtable(_pmd); > - > - _pmd = folio_mk_pmd(folio, vma->vm_page_prot); > - _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); > - > - spin_lock(pmd_ptl); > - BUG_ON(!pmd_none(*pmd)); > - folio_add_new_anon_rmap(folio, vma, address, RMAP_EXCLUSIVE); > - folio_add_lru_vma(folio, vma); > - pgtable_trans_huge_deposit(mm, pmd, pgtable); > - set_pmd_at(mm, address, pmd, _pmd); > - update_mmu_cache_pmd(vma, address, pmd); > - deferred_split_folio(folio, false); > - spin_unlock(pmd_ptl); > + if (order == HPAGE_PMD_ORDER) { > + pgtable = pmd_pgtable(_pmd); > + _pmd = folio_mk_pmd(folio, vma->vm_page_prot); > + _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); > + > + spin_lock(pmd_ptl); > + BUG_ON(!pmd_none(*pmd)); > + folio_add_new_anon_rmap(folio, vma, _address, RMAP_EXCLUSIVE); > + folio_add_lru_vma(folio, vma); > + pgtable_trans_huge_deposit(mm, pmd, pgtable); > + set_pmd_at(mm, address, pmd, _pmd); > + update_mmu_cache_pmd(vma, address, pmd); > + deferred_split_folio(folio, false); > + spin_unlock(pmd_ptl); > + } else { //mTHP (Nit: use '/* xxx */' format) > + mthp_pte = mk_pte(&folio->page, vma->vm_page_prot); > + mthp_pte = maybe_mkwrite(pte_mkdirty(mthp_pte), vma); > + > + spin_lock(pmd_ptl); > + folio_ref_add(folio, (1 << order) - 1); > + folio_add_new_anon_rmap(folio, vma, _address, RMAP_EXCLUSIVE); > + folio_add_lru_vma(folio, vma); > + set_ptes(vma->vm_mm, _address, pte, mthp_pte, (1 << order)); You still used the unmapped pte? Looks incorrect to me. > + update_mmu_cache_range(NULL, vma, _address, pte, (1 << order)); > + > + smp_wmb(); /* make pte visible before pmd */ > + pmd_populate(mm, pmd, pmd_pgtable(_pmd)); > + spin_unlock(pmd_ptl); > + } > > folio = NULL; > > @@ -1364,31 +1383,58 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, > { > pmd_t *pmd; > pte_t *pte, *_pte; > + int i; > int result = SCAN_FAIL, referenced = 0; > int none_or_zero = 0, shared = 0; > struct page *page = NULL; > struct folio *folio = NULL; > unsigned long _address; > + unsigned long enabled_orders; > spinlock_t *ptl; > int node = NUMA_NO_NODE, unmapped = 0; > + bool is_pmd_only; > bool writable = false; > - > + int chunk_none_count = 0; > + int scaled_none = khugepaged_max_ptes_none >> (HPAGE_PMD_ORDER - KHUGEPAGED_MIN_MTHP_ORDER); > + unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0; > VM_BUG_ON(address & ~HPAGE_PMD_MASK); > > result = find_pmd_or_thp_or_none(mm, address, &pmd); > if (result != SCAN_SUCCEED) > goto out; > > + bitmap_zero(cc->mthp_bitmap, MAX_MTHP_BITMAP_SIZE); > + bitmap_zero(cc->mthp_bitmap_temp, MAX_MTHP_BITMAP_SIZE); > memset(cc->node_load, 0, sizeof(cc->node_load)); > nodes_clear(cc->alloc_nmask); > + > + enabled_orders = thp_vma_allowable_orders(vma, vma->vm_flags, > + tva_flags, THP_ORDERS_ALL_ANON); > + > + is_pmd_only = (enabled_orders == (1 << HPAGE_PMD_ORDER)); > + > pte = pte_offset_map_lock(mm, pmd, address, &ptl); > if (!pte) { > result = SCAN_PMD_NULL; > goto out; > } > > - for (_address = address, _pte = pte; _pte < pte + HPAGE_PMD_NR; > - _pte++, _address += PAGE_SIZE) { > + for (i = 0; i < HPAGE_PMD_NR; i++) { > + /* > + * we are reading in KHUGEPAGED_MIN_MTHP_NR page chunks. if > + * there are pages in this chunk keep track of it in the bitmap > + * for mTHP collapsing. > + */ > + if (i % KHUGEPAGED_MIN_MTHP_NR == 0) { > + if (chunk_none_count <= scaled_none) > + bitmap_set(cc->mthp_bitmap, > + i / KHUGEPAGED_MIN_MTHP_NR, 1); > + > + chunk_none_count = 0; > + } > + > + _pte = pte + i; > + _address = address + i * PAGE_SIZE; > pte_t pteval = ptep_get(_pte); > if (is_swap_pte(pteval)) { > ++unmapped; > @@ -1411,10 +1457,11 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, > } > } > if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { > + ++chunk_none_count; > ++none_or_zero; > if (!userfaultfd_armed(vma) && > - (!cc->is_khugepaged || > - none_or_zero <= khugepaged_max_ptes_none)) { > + (!cc->is_khugepaged || !is_pmd_only || > + none_or_zero <= khugepaged_max_ptes_none)) { > continue; > } else { > result = SCAN_EXCEED_NONE_PTE; > @@ -1510,6 +1557,7 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, > address))) > referenced++; > } > + > if (!writable) { > result = SCAN_PAGE_RO; > } else if (cc->is_khugepaged && > @@ -1522,8 +1570,12 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, > out_unmap: > pte_unmap_unlock(pte, ptl); > if (result == SCAN_SUCCEED) { > - result = collapse_huge_page(mm, address, referenced, > - unmapped, cc, mmap_locked, HPAGE_PMD_ORDER, 0); > + result = khugepaged_scan_bitmap(mm, address, referenced, unmapped, cc, > + mmap_locked, enabled_orders); > + if (result > 0) > + result = SCAN_SUCCEED; > + else > + result = SCAN_FAIL; > } > out: > trace_mm_khugepaged_scan_pmd(mm, &folio->page, writable, referenced, > @@ -2479,11 +2531,13 @@ static int khugepaged_collapse_single_pmd(unsigned long addr, > fput(file); > if (result == SCAN_PTE_MAPPED_HUGEPAGE) { > mmap_read_lock(mm); > + *mmap_locked = true; > if (khugepaged_test_exit_or_disable(mm)) > goto end; > result = collapse_pte_mapped_thp(mm, addr, > !cc->is_khugepaged); > mmap_read_unlock(mm); > + *mmap_locked = false; > } > } else { > result = khugepaged_scan_pmd(mm, vma, addr,