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([2620:10d:c092:500::6:8e63]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ab78e3e212dsm1136599566b.147.2025.02.12.09.04.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Feb 2025 09:04:44 -0800 (PST) Message-ID: <9ade1f26-1642-48b3-b7e4-ba571892c7d6@gmail.com> Date: Wed, 12 Feb 2025 17:04:43 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC v2 7/9] khugepaged: add mTHP support To: Nico Pache , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org Cc: ryan.roberts@arm.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, cl@gentwo.org, vbabka@suse.cz, mhocko@suse.com, apopple@nvidia.com, dave.hansen@linux.intel.com, will@kernel.org, baohua@kernel.org, jack@suse.cz, srivatsa@csail.mit.edu, haowenchao22@gmail.com, hughd@google.com, aneesh.kumar@kernel.org, yang@os.amperecomputing.com, peterx@redhat.com, ioworker0@gmail.com, wangkefeng.wang@huawei.com, ziy@nvidia.com, jglisse@google.com, surenb@google.com, vishal.moola@gmail.com, zokeefe@google.com, zhengqi.arch@bytedance.com, jhubbard@nvidia.com, 21cnbao@gmail.com, willy@infradead.org, kirill.shutemov@linux.intel.com, david@redhat.com, aarcange@redhat.com, raquini@redhat.com, dev.jain@arm.com, sunnanyong@huawei.com, audra@redhat.com, akpm@linux-foundation.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, tiwai@suse.de, Johannes Weiner References: <20250211003028.213461-1-npache@redhat.com> <20250211003028.213461-8-npache@redhat.com> Content-Language: en-US From: Usama Arif In-Reply-To: <20250211003028.213461-8-npache@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: CF3691C001D X-Stat-Signature: inkjp7shgx8r9goux9x7kfpokd9fpk1w X-Rspamd-Server: rspam03 X-HE-Tag: 1739379886-139527 X-HE-Meta: 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 2561Zlie 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 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 11/02/2025 00:30, Nico Pache wrote: > Introduce the ability for khugepaged to collapse to different mTHP sizes. > While scanning a PMD range for potential collapse candidates, keep track > of pages in MIN_MTHP_ORDER chunks via a bitmap. Each bit represents a > utilized region of order MIN_MTHP_ORDER ptes. 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, 83 insertions(+), 39 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index c8048d9ec7fb..cd310989725b 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1127,13 +1127,14 @@ 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); > > /* > @@ -1148,12 +1149,13 @@ 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; > @@ -1171,13 +1173,14 @@ 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 > @@ -1187,7 +1190,7 @@ 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 */ > @@ -1198,11 +1201,12 @@ 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 > @@ -1216,10 +1220,10 @@ 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; > @@ -1248,8 +1252,8 @@ 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); > if (unlikely(result != SCAN_SUCCEED)) > goto out_up_write; > @@ -1260,20 +1264,37 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, > * write. > */ > __folio_mark_uptodate(folio); > - pgtable = pmd_pgtable(_pmd); > - > - _pmd = mk_huge_pmd(&folio->page, 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 = mk_huge_pmd(&folio->page, 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 > + 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); > + spin_lock(pte_ptl); > + set_ptes(vma->vm_mm, _address, pte, mthp_pte, (1 << order)); > + update_mmu_cache_range(NULL, vma, _address, pte, (1 << order)); > + spin_unlock(pte_ptl); > + smp_wmb(); /* make pte visible before pmd */ > + pmd_populate(mm, pmd, pmd_pgtable(_pmd)); > + deferred_split_folio(folio, false); Hi Nico, This patch will have the same issue as the one I pointed out in https://lore.kernel.org/all/82b9efd1-f2a6-4452-b2ea-6c163e17cdf7@gmail.com/ ?