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Thu, 15 May 2025 03:05:27 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.88.116]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CFA411800268; Thu, 15 May 2025 03:05:11 +0000 (UTC) From: Nico Pache To: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org 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, baohua@kernel.org, willy@infradead.org, peterx@redhat.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, 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 Subject: [PATCH v6 07/12] khugepaged: add mTHP support Date: Wed, 14 May 2025 21:03:07 -0600 Message-ID: <20250515030312.125567-8-npache@redhat.com> In-Reply-To: <20250515030312.125567-7-npache@redhat.com> References: <20250515030312.125567-1-npache@redhat.com> <20250515030312.125567-2-npache@redhat.com> <20250515030312.125567-3-npache@redhat.com> <20250515030312.125567-4-npache@redhat.com> <20250515030312.125567-5-npache@redhat.com> <20250515030312.125567-6-npache@redhat.com> <20250515030312.125567-7-npache@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Stat-Signature: 8s9zhxmmw8o6kdaz1ncxgyhx8miewxgf X-Rspam-User: X-Rspamd-Queue-Id: 9105440007 X-Rspamd-Server: rspam06 X-HE-Tag: 1747278335-266630 X-HE-Meta: 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 1HVXalkg Y4LRHhLdNxygRCmPIzHkEdXKbNn3K1rFZ0MUhz7tmbHFGHE6GGEu2zLS1MOmk4xJXepUgeBVwRkEMeln2FkKci8zC+TFO6gMFr0ij/XMWCeHd/1nTznolP0KGZioNg39HMFCgKmBtRRROTqfRhl1VIVPauIVaSRsh6CiMYPzWeQc0swkN+13xHNZvIGKUluAn6kEMjyPdexVs6KPNv7qKZzSHabaMqb0i+dxJmtV+7aRQO86bWW4cRzzGBWIjhy1O5PB10nNthcMrsaDL05/rM685BjlnXHI5qQQ26ruF3WnH4c+cNLGdhU/fjbnnsK6VDN+PvKz3wYIx/R4bmwe62ogfIV/gb5f+RdRD0MDRlFXoScyHRij5BTsK3vIK9KziRThJMnKHoYT29l0Vt+21CdzAmg== 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: 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. For non PMD collapse we much leave the anon VMA write locked until after we collapse the mTHP Signed-off-by: Nico Pache --- mm/khugepaged.c | 136 +++++++++++++++++++++++++++++++++--------------- 1 file changed, 95 insertions(+), 41 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 044fec869b50..afad75fc01b7 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1138,13 +1138,14 @@ 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 = NULL, 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); @@ -1160,12 +1161,13 @@ 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; @@ -1183,13 +1185,14 @@ 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 @@ -1199,7 +1202,7 @@ 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 */ @@ -1210,11 +1213,12 @@ 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 @@ -1228,18 +1232,16 @@ 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; } if (unlikely(result != SCAN_SUCCEED)) { - if (pte) - pte_unmap(pte); spin_lock(pmd_ptl); BUG_ON(!pmd_none(*pmd)); /* @@ -1254,17 +1256,17 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, } /* - * All pages are isolated and locked so anon_vma rmap - * can't run anymore. + * For PMD collapse all pages are isolated and locked so anon_vma + * rmap can't run anymore */ - anon_vma_unlock_write(vma->anon_vma); + if (order == HPAGE_PMD_ORDER) + 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); - pte_unmap(pte); + vma, _address, pte_ptl, + &compound_pagelist, order); if (unlikely(result != SCAN_SUCCEED)) - goto out_up_write; + goto out_unlock_anon_vma; /* * The smp_wmb() inside __folio_mark_uptodate() ensures the @@ -1272,25 +1274,45 @@ 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 collapse */ + 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)); + 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; result = SCAN_SUCCEED; +out_unlock_anon_vma: + if (order != HPAGE_PMD_ORDER) + anon_vma_unlock_write(vma->anon_vma); out_up_write: + if (pte) + pte_unmap(pte); mmap_write_unlock(mm); out_nolock: *mmap_locked = false; @@ -1366,31 +1388,57 @@ 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; @@ -1413,10 +1461,11 @@ 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; @@ -1512,6 +1561,7 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, address))) referenced++; } + if (!writable) { result = SCAN_PAGE_RO; } else if (cc->is_khugepaged && @@ -1524,8 +1574,12 @@ 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, writable, referenced, -- 2.49.0