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([2620:10d:c092:500::6:b6e0]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a7acad91005sm794069066b.173.2024.07.31.10.08.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 31 Jul 2024 10:08:31 -0700 (PDT) Message-ID: <042be214-e51c-4c69-9839-329f206dc8f8@gmail.com> Date: Wed, 31 Jul 2024 18:08:31 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/6] mm: don't remap unused subpages when splitting isolated thp To: Rik van Riel , akpm@linux-foundation.org, linux-mm@kvack.org Cc: hannes@cmpxchg.org, shakeel.butt@linux.dev, roman.gushchin@linux.dev, yuzhao@google.com, david@redhat.com, baohua@kernel.org, ryan.roberts@arm.com, rppt@kernel.org, willy@infradead.org, cerasuolodomenico@gmail.com, corbet@lwn.net, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@meta.com, Shuang Zhai References: <20240730125346.1580150-1-usamaarif642@gmail.com> <20240730125346.1580150-5-usamaarif642@gmail.com> <20df6650c834b3d2d6e5d7062876ee6a1e997dba.camel@surriel.com> Content-Language: en-US From: Usama Arif In-Reply-To: <20df6650c834b3d2d6e5d7062876ee6a1e997dba.camel@surriel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: y1dqp13gyobynh5rqd9zdae755b3pp7w X-Rspam-User: X-Rspamd-Queue-Id: 3E7B54000F X-Rspamd-Server: rspam02 X-HE-Tag: 1722445714-140873 X-HE-Meta: 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 GGt68H9/ VZK270Q1blDUUsf5oNhz0kwzQv92NnF8H1KKqO0sKqPn4W7HQ/NI4Ci+S9szyHnZJmwUiqcWwfO1pDcxOTvmD8bOdc8gNn0VDJwGZ5dKLJtPtjCWnlPvtmtn8r0dMMZZ23k99SnrUXRIHpaBNnTYfSSIuhXtYJht7NRYm2g7i1GqkBn+36e0aWTWgnXjl/7pUTy2T3/+bGpzpJJBOQA1zR3igGUu849Xi+2MjI7MGGSj27SrMvVDxcIwrf0KTJhtpF0KqUlDSYW/qZweGsIVi7HSj+0Gzu7Nfo6RY2NAumeaVRpHxcdhBuQN6jGW1IDs+N32s8UGr1249I7X4wIJppN+6oZBX+DFes6gPQp6bBDsKw53hM+275rZQqYWego1OP5TXCKcoelwH3f9B5jRjxFOQ4hQ4LSvheCtOmpgE7IZrKgY= 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 30/07/2024 19:07, Rik van Riel wrote: > On Tue, 2024-07-30 at 13:46 +0100, Usama Arif wrote: >> >> + /* >> + * The pmd entry mapping the old thp was flushed and the pte >> mapping >> + * this subpage has been non present. Therefore, this >> subpage is >> + * inaccessible. We don't need to remap it if it contains >> only zeros. >> + */ >> + addr = kmap_local_page(page); >> + dirty = memchr_inv(addr, 0, PAGE_SIZE); >> + kunmap_local(addr); >> + >> + if (dirty) >> + return false; >> > > A minor nitpick here. The word dirty has a few different meanings > in memory management already. > > Could it be clearer to use something like "contains_data" ? > Thanks, yes makes much more sense, will use contains_data in the next revision.