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Sat, 26 Oct 2024 09:34:07 +0800 Message-ID: <5d0b94b9-44e0-43e1-bec6-d6efd40deec1@huawei.com> Date: Sat, 26 Oct 2024 09:34:06 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH resend 1/2] mm: always use base address when clear gigantic page To: Andrew Morton CC: David Hildenbrand , Matthew Wilcox , Muchun Song , "Huang, Ying" , References: <20241025004456.3435808-1-wangkefeng.wang@huawei.com> <20241025155615.bd9570fd6147ebd764c858fd@linux-foundation.org> Content-Language: en-US From: Kefeng Wang In-Reply-To: <20241025155615.bd9570fd6147ebd764c858fd@linux-foundation.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpemf100008.china.huawei.com (7.185.36.138) X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 6C28D100002 X-Stat-Signature: ho1hmjh5djwmujp46crs3z6kadh9pico X-HE-Tag: 1729906415-943131 X-HE-Meta: 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 abi+MtO9 eq5JJ+seSPOJjXeVHNtcZYsaaPzmbqiJf3mGbo9cb63vaJpVtzBUDTaAOxH7BXTE+a0cgF01Uabk0meXPc97yPiq/RhxBz2rWgL/tedJ2n4dvzPQft7HPxp3obA+BJA+SUwKZUt5DFKWx9HH5dbP1IQ9Ni/4rVsSw1dIeeZmBX1R9bl4DPptLjV1pU4ARqvTGw9oGqIM4ODH8SRP0QSS2naHm9NjIrlxOuY7vgWoKyfqV4ax9DG+DfLOsAHhFOr7TE7BMbcRiayRo89ZfTVwTUQML2Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, 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 2024/10/26 6:56, Andrew Morton wrote: > On Fri, 25 Oct 2024 08:44:55 +0800 Kefeng Wang wrote: > >> When clear gigantic page, it zeros page from the first subpage to >> the last subpage, that is, aligned base address is needed in it, >> and we don't need to aligned down the address in the caller as the >> real address will be passed to process_huge_page(). > > Matthew just told us that folios con't have subpages > (https://lkml.kernel.org/r/ZxsRCyBSO-C27Uzn@casper.infradead.org). > OK, will change subpage to page. > Please carefully describe the impact of this change. I think it's > "small cleanup and optimization?" > > Also, I find the changelog rather hard to follow. I think we're adding > the alignment operation to the callee and hence removing it from the > caller? > Sorry for the confuse, there is some different between gigantic page(nr_pages > MAX_ORDER_NR_PAGE) and non-gigantic page, 1) for gigantic page, it always clear/copy page from the fist page to the last page, see copy_user_gigantic_page/clear_gigantic_page, but if directly pass addr_hint which maybe not the address of the first page, then if arch's code use this addr_hint to flush cache, it may flush the wrong cache. 2) for non-gigantic page, it calculate the base address inside, see process_huge_page, if we passed the wrong addr_hint, it only has performance impact(not sure, but at least no different on arm64), no function impact. Will update the change and resend.