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[2003:cb:c745:2300:653:c844:4858:570f]) by smtp.gmail.com with ESMTPSA id cr12-20020a05600004ec00b00341ce80ea66sm17810206wrb.82.2024.04.17.08.02.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Apr 2024 08:02:20 -0700 (PDT) Message-ID: <2062c2d1-4ebb-4a40-89f9-3083e6912301@redhat.com> Date: Wed, 17 Apr 2024 17:02:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] mm/vmscan: avoid split PMD-mapped THP during shrink_folio_list() To: Lance Yang , akpm@linux-foundation.org Cc: willy@infradead.org, maskray@google.com, ziy@nvidia.com, ryan.roberts@arm.com, 21cnbao@gmail.com, mhocko@suse.com, fengwei.yin@intel.com, zokeefe@google.com, shy828301@gmail.com, xiehuan09@gmail.com, wangkefeng.wang@huawei.com, songmuchun@bytedance.com, peterx@redhat.com, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240417141111.77855-1-ioworker0@gmail.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20240417141111.77855-1-ioworker0@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 8F38810000D X-Stat-Signature: xu4gur8a7x98rziomhtwmtqo5zrgkfht X-Rspam-User: X-HE-Tag: 1713366145-372973 X-HE-Meta: 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 SjN7e666 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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 17.04.24 16:11, Lance Yang wrote: > When the user no longer requires the pages, they would use madvise(madv_free) > to mark the pages as lazy free. IMO, they would not typically rewrite to the > given range. > > At present, a PMD-mapped THP marked as lazyfree during shrink_folio_list() > is unconditionally split, which may be unnecessary. If the THP is exclusively > mapped and clean, and the PMD associated with it is also clean, then we can > attempt to remove the PMD mapping from it. This change will improve the > efficiency of memory reclamation in this case. > > On an Intel i5 CPU, reclaiming 1GiB of PMD-mapped THPs using > mem_cgroup_force_empty() results in the following runtimes in seconds > (shorter is better): > > -------------------------------------------- > | Old | New | Change | > -------------------------------------------- > | 0.683426 | 0.049197 | -92.80% | > -------------------------------------------- > > Signed-off-by: Lance Yang > --- > include/linux/huge_mm.h | 1 + > include/linux/rmap.h | 1 + > mm/huge_memory.c | 2 +- > mm/rmap.c | 81 +++++++++++++++++++++++++++++++++++++++++ > mm/vmscan.c | 7 ++++ > 5 files changed, 91 insertions(+), 1 deletion(-) > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index 7cd07b83a3d0..02a71c05f68a 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -36,6 +36,7 @@ bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr, > int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > pmd_t *pmd, unsigned long addr, pgprot_t newprot, > unsigned long cp_flags); > +inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd); > > vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write); > vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write); > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > index 0f906dc6d280..8c2f45713351 100644 > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -100,6 +100,7 @@ enum ttu_flags { > * do a final flush if necessary */ > TTU_RMAP_LOCKED = 0x80, /* do not grab rmap lock: > * caller holds it */ > + TTU_LAZYFREE_THP = 0x100, /* avoid split PMD-mapped THP */ > }; > > #ifdef CONFIG_MMU > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 58f2c4745d80..309fba9624c2 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1801,7 +1801,7 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > return ret; > } > > -static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd) > +inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd) > { > pgtable_t pgtable; > > diff --git a/mm/rmap.c b/mm/rmap.c > index 2608c40dffad..4994f9e402d4 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -77,6 +77,7 @@ > #include > > #include > +#include > > #define CREATE_TRACE_POINTS > #include > @@ -1606,6 +1607,80 @@ void folio_remove_rmap_pmd(struct folio *folio, struct page *page, > #endif > } > > +static bool __try_to_unmap_lazyfree_thp(struct vm_area_struct *vma, > + unsigned long address, > + struct folio *folio) > +{ > + spinlock_t *ptl; > + pmd_t *pmdp, orig_pmd; > + struct mmu_notifier_range range; > + struct mmu_gather tlb; > + struct mm_struct *mm = vma->vm_mm; > + struct page *page; > + bool ret = false; > + > + VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); > + VM_WARN_ON_FOLIO(folio_test_swapbacked(folio), folio); > + VM_WARN_ON_FOLIO(!folio_test_pmd_mappable(folio), folio); > + VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio); > + > + /* > + * If we encounter a PMD-mapped THP that marked as lazyfree, we > + * will try to unmap it without splitting. > + * > + * The folio exclusively mapped should only have two refs: > + * one from the isolation and one from the rmap. > + */ > + if (folio_entire_mapcount(folio) != 1 || folio_test_dirty(folio) || > + folio_ref_count(folio) != 2) folio_mapcount() == 1 is a bit nicer. Bit I assume you can drop that completely and only check the refcount? > + return false; > + > + pmdp = mm_find_pmd(mm, address); > + if (unlikely(!pmdp)) > + return false; > + if (pmd_dirty(*pmdp)) > + return false; > + > + tlb_gather_mmu(&tlb, mm); > + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, > + address & HPAGE_PMD_MASK, > + (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE); > + mmu_notifier_invalidate_range_start(&range); > + > + ptl = pmd_lock(mm, pmdp); > + orig_pmd = *pmdp; > + if (unlikely(!pmd_present(orig_pmd) || !pmd_trans_huge(orig_pmd))) > + goto out; > + > + page = pmd_page(orig_pmd); > + if (unlikely(page_folio(page) != folio)) > + goto out; > + > + orig_pmd = pmdp_huge_get_and_clear(mm, address, pmdp); > + tlb_remove_pmd_tlb_entry(&tlb, pmdp, address); Until this point, the page could have been pinned (including GUP-fast) and we might be in trouble if we drop it. -- Cheers, David / dhildenb