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[2003:cb:c721:8100:177e:1983:5478:64ec]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38221679dbdsm2907816f8f.64.2024.11.15.02.22.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 15 Nov 2024 02:22:32 -0800 (PST) Message-ID: <77b1eddf-7c1b-43e9-9352-229998ce3fc7@redhat.com> Date: Fri, 15 Nov 2024 11:22:31 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 4/9] mm: introduce skip_none_ptes() To: Qi Zheng Cc: jannh@google.com, hughd@google.com, willy@infradead.org, muchun.song@linux.dev, vbabka@kernel.org, akpm@linux-foundation.org, peterx@redhat.com, mgorman@suse.de, catalin.marinas@arm.com, will@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, x86@kernel.org, lorenzo.stoakes@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, zokeefe@google.com, rientjes@google.com References: <574bc9b646c87d878a5048edb63698a1f8483e10.1731566457.git.zhengqi.arch@bytedance.com> <617a063e-bd84-4da5-acf4-6ff516512055@bytedance.com> <253e5fd0-7e98-43fd-b0d7-8a5b739ae4aa@bytedance.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: ADBA780006 X-Stat-Signature: 4ooa9jz5xajjec79e4jh9r337sa79s6s X-Rspam-User: X-HE-Tag: 1731666072-203175 X-HE-Meta: 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 DPQbPamo tP7fWf/Sgq9MdsCOI1QpwPo9D4z9lDfBvAiwJG6qfMW2GIPYJsPyUj25XTYYfmHX9iyVdWa4Zbs6e9cNmHYuYHV/1kd0xjzd0/uFhwP3k2ueuY3EnFSfhsRhPUKHX2EiouN6Ty+Dj0f51Hf6UJwp6iGfJtDR2T43/FONndBiU/jEr5k973EGLuXytHTxYNH606qnxHYunoNUP0UbEnBoHTQZrKJQhpsRYYO3sXdTiiUHAZVHIoNm/kOHmDV6cOCGUPBRnxpaIzu+rhw0L4UT+hpJ1/hrJLqSIPIwxhG4YWfSzuK9p2ofhTLYo1IElCK652qHLTib2/YHH0o+n05oAdTvcwa6nFmxrXaGEbxmdldV4/skpmsS7R6maA1RNjmy8kVad5BU61bxBbfbhIS+qWjNjTgiDDc2Oti8WNAO1JxLRNpYDqfUnmaIM4rLfbcG0r5exJmeaFYrF/H0aR8k09cgqLA== 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: >>> *nr_skip = nr; >>> >>> and then: >>> >>> zap_pte_range >>> --> nr = do_zap_pte_range(tlb, vma, pte, addr, end, details, &skip_nr, >>>                          rss, &force_flush, &force_break); >>>       if (can_reclaim_pt) { >>>           none_nr += count_pte_none(pte, nr); >>>           none_nr += nr_skip; >>>       } >>> >>> Right? >> >> Yes. I did not look closely at the patch that adds the counting of > > Got it. > >> pte_none though (to digest why it is required :) ). > > Because 'none_nr == PTRS_PER_PTE' is used in patch #7 to detect > empty PTE page. Okay, so the problem is that "nr" would be "all processed entries" but there are cases where we "process an entry but not zap it". What you really only want to know is "was any entry not zapped", which could be a simple input boolean variable passed into do_zap_pte_range? Because as soon as any entry was processed but no zapped, you can immediately give up on reclaiming that table. > > Looking forward to your more review feedback on this series. Thanks for all your hard work on this, I'm only able to make slow progress because I keep getting distracted by all different kinds of things :( -- Cheers, David / dhildenb