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AJvYcCU6xuJgb7bsgJYqiGUwXn448yc0D6XClO74VQSbxTl9EjBV42HPpDufxYSUY/miYYO4Hr/cPbCxnqDApC9FpMv2l5s= X-Gm-Message-State: AOJu0Yx0dy0kJwFCk7yj0pqzN6CmDuMOW+GOH2UagarOa7mBdNt4kdUY NHJ0PNfx50xGXwIey1GJezXI5QXnos4G+T7uYmoPErTQL11l5sQU X-Google-Smtp-Source: AGHT+IFXLjhPaCj5Z8Oe14oldl4gZO8dRpoP10oLa1z/M5Kni5pv9yJJDxahJGUprS04gno+V7T7Pg== X-Received: by 2002:a17:902:d481:b0:1f6:8973:e4b0 with SMTP id d9443c01a7336-1f68973ff30mr33527995ad.39.1717496775133; Tue, 04 Jun 2024 03:26:15 -0700 (PDT) Received: from [192.168.255.10] ([43.132.141.20]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1f632419187sm79631125ad.287.2024.06.04.03.26.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Jun 2024 03:26:14 -0700 (PDT) Message-ID: <4d299245-3166-4810-b22b-2a5b4f54a049@gmail.com> Date: Tue, 4 Jun 2024 18:26:11 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/10] mm/ksm: reduce the flush action for ksm merging page To: David Hildenbrand , alexs@kernel.org, Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, izik.eidus@ravellosystems.com, willy@infradead.org, aarcange@redhat.com, chrisw@sous-sol.org, hughd@google.com References: <20240604042454.2012091-1-alexs@kernel.org> <20240604042454.2012091-2-alexs@kernel.org> <9ca730ce-2b2f-42d2-8c7a-78735a995c64@redhat.com> Content-Language: en-US From: Alex Shi In-Reply-To: <9ca730ce-2b2f-42d2-8c7a-78735a995c64@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 7DE2F18000F X-Stat-Signature: efqdbkmmanft76t1mk4krytoigygk6d8 X-HE-Tag: 1717496776-560035 X-HE-Meta: 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 AXjZ4Wqx 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, 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 6/4/24 4:07 PM, David Hildenbrand wrote: > On 04.06.24 06:24, alexs@kernel.org wrote: >> From: "Alex Shi (tencent)" >> >> We can put off the flush action util a merging is realy coming. That >> could reduce some unmerge page flushing. >> BTW, flushing only do at arm, mips and few other archs. >> > > I'm no expert on that flushing, but I thought we would have to do the flushing before accessing page content -- before calculating the checksum etc. > > Now you would only do it before the pages_identical() check, but not when calculating the checksum. > Hi David, Thanks a lot for comments! If calc_checksum() is wrong before pages_idential(), (that's just after page was write_protected, that's a real guarantee for page context secured) pages_identical could recheck and make thing right. And as to 2 flush functions here, I didn't see the guarantee for other writer from any other place. So maybe we should remove these flush action? Thanks Alex