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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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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.