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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id 22-20020a810b16000000b0054fae5ed408sm2677063ywl.45.2023.04.16.12.51.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 16 Apr 2023 12:51:55 -0700 (PDT) Date: Sun, 16 Apr 2023 12:51:46 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Zi Yan cc: "Matthew Wilcox (Oracle)" , Yang Shi , Yu Zhao , linux-mm@kvack.org, "Kirill A . Shutemov" , Ryan Roberts , =?ISO-8859-15?Q?Michal_Koutn=FD?= , Roman Gushchin , Zach O'Keefe , Andrew Morton , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v3 6/7] mm: truncate: split huge page cache page to a non-zero order if possible. In-Reply-To: <9dd96da-efa2-5123-20d4-4992136ef3ad@google.com> Message-ID: <86864d6c-39d3-d26f-278f-b96e14884541@google.com> References: <20230403201839.4097845-1-zi.yan@sent.com> <20230403201839.4097845-7-zi.yan@sent.com> <9dd96da-efa2-5123-20d4-4992136ef3ad@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Stat-Signature: ojdwowckma7h94odzcgyhxohhiqzq7wy X-Rspam-User: X-Rspamd-Queue-Id: 5236E1C000C X-Rspamd-Server: rspam06 X-HE-Tag: 1681674717-274744 X-HE-Meta: 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 sfTifHQ5 sgHNnB3MBsHwKw2SoSRbOXBCkX/Q8wZNnbUAK1mHuvfM9OYwBIM3/W/uH7xlU76obbfMmWKNY1K9vmC+/8Z75lZmlxF5ZQKcBKBcwgAnwAL4E0/dxufOV6rlLTvgQDAbrG5ZX1xJN4Vp2lvYcCvfD/U3a/cjHG+7eDLLXHlhq9aSYaykEIaFYf/gwpWC6SJQiOpOaRi+6x8t2SpYj7RJjt+mECwUYFls/zyIgQ5PEyGY2LugOke5GLma3aCi1QNuyZ8s3Ff8l+wfudmWffDkqfVBjwOUhUDmnHKglRx4yW8MjJRSR9x/1JDWbgMqkbjUh1pc/jiLKhAgRANQ1w+7A2CU8c2JaGXrVZFOceTBd3/ggQKzW8fPlo4unVVITQwvdA/HpECq/xu+8ZaYbmtvuGb5/jg== 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: > As this code stands, truncate a 2M huge page at 1M and you get two 1M > pieces (one then discarded) - nice; but truncate it at 1M+1 and you get > lots of order 2 (forced up from 1) pieces. Seems weird, and not worth > the effort. I've probably said that wrong: truncate at 1M+1 and you'd get lots of order 0 pieces. Hugh