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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1734462722; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mHysgArAVn72bWhos4LTZ6OG9oQKx3cxQ/NDDOJ8hqM=; b=Nqh1GnKlWQUwvPe/nqFxHV4/Be8DcWHdF5Oi5G0BlV2YVAosz6fHTwdCs9+Mi499qBFZtb 4+3fhrZOej0ZcmfOldi0GG8vvux2aSEWoPrdtNHaXd7NVzEPWENhdQp7+68RopmXHkttYS pLbg4iD18BJ8g9WR4zP4JeQWZmpWmAw= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A6833FEC; Tue, 17 Dec 2024 11:12:57 -0800 (PST) Received: from [10.57.91.184] (unknown [10.57.91.184]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A47043F528; Tue, 17 Dec 2024 11:12:23 -0800 (PST) Message-ID: <8f1ef412-6f43-4346-bbfd-84431f3a5488@arm.com> Date: Tue, 17 Dec 2024 19:12:21 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 01/12] khugepaged: Rename hpage_collapse_scan_pmd() -> ptes() Content-Language: en-GB To: Zi Yan , Dev Jain Cc: Matthew Wilcox , akpm@linux-foundation.org, david@redhat.com, kirill.shutemov@linux.intel.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, cl@gentwo.org, vbabka@suse.cz, mhocko@suse.com, apopple@nvidia.com, dave.hansen@linux.intel.com, will@kernel.org, baohua@kernel.org, jack@suse.cz, srivatsa@csail.mit.edu, haowenchao22@gmail.com, hughd@google.com, aneesh.kumar@kernel.org, yang@os.amperecomputing.com, peterx@redhat.com, ioworker0@gmail.com, wangkefeng.wang@huawei.com, jglisse@google.com, surenb@google.com, vishal.moola@gmail.com, zokeefe@google.com, zhengqi.arch@bytedance.com, jhubbard@nvidia.com, 21cnbao@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20241216165105.56185-1-dev.jain@arm.com> <20241216165105.56185-2-dev.jain@arm.com> <0a33f5c1-c974-4d4a-94dd-6741399e186e@arm.com> <35E34233-3435-4873-A82C-A1DFBD0AFC55@nvidia.com> From: Ryan Roberts In-Reply-To: <35E34233-3435-4873-A82C-A1DFBD0AFC55@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: op4eemc6hcytow1fxaaqt3a9yk4ypyez X-Rspam-User: X-Rspamd-Queue-Id: 2F9D4140010 X-Rspamd-Server: rspam08 X-HE-Tag: 1734462729-564269 X-HE-Meta: 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 M9oM2frM 1QZ4429XE8XQmgNZBXeKpWg/AlLmD7Q2fV2dh2wgoDuZ9lB9kELsrirXXlJXrwTtoPwGG4xCDmJZ0A24wOfMlPO0yIdBh4zzEypYXBM7wtUB+5QzDIZ/fkAhy+CPWvAgBg3rGRkcIMpTYj6+JWDWHa70GOwuvawIJxc8T/qK8M5BFudMU6yajPLa/O1DnTJrj+hBovRbOzX30N/71EI6hOrB/ch+rOpE9z4LavZbgCsYkjbxE719TSZ4aCSi0tERa3NcLlr9CyWoYcSsKHVeE/gGIb6Bkbz+71jxnJ3PJZ5UlhAHUo4S9EDa7fCnMQutVLHiE+3aMrYKNPYUPnDi+M1Db2sNgHmkVLbz5C79bdMm3Z8pczpIsdk/27Y69iAdulEDJ 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 17/12/2024 18:11, Zi Yan wrote: > On 17 Dec 2024, at 1:43, Ryan Roberts wrote: > >> On 17/12/2024 04:18, Matthew Wilcox wrote: >>> On Mon, Dec 16, 2024 at 10:20:54PM +0530, Dev Jain wrote: >>>> -static int hpage_collapse_scan_pmd(struct mm_struct *mm, >>>> +static int hpage_collapse_scan_ptes(struct mm_struct *mm, >>> >>> i don't think this is necessary at all. you're scanning a pmd. >>> you might not be scanning in order to collapse to a pmd, but pmd >>> is the level you're scanning at. >>> >> >> Sorry Matthew, I don't really understand this statement. Prior to the change we >> were scanning all PTE entries in a PTE table with the aim of collapsing to a PMD >> entry. After the change we are scanning some PTE entries in a PTE table with the >> aim of collapsing to either to a multi-PTE-mapped folio or a single-PMD-mapped >> folio. >> >> So personally I think "scan_pmd" was a misnomer even before the change - we are >> scanning the ptes. > > But there are still a lot of scan_pmd code in the function, for example, > VM_BUG_ON(address & ~HPAGE_PMD_MASK), _pte < pte + HPAGE_PMD_NR in the function. > These need to be changed along with function renaming. If after the change only > a subset of PTEs are scanned within a PMD, maybe a scan_range parameter can be > added. Oh I see; I think your and Matthew's point is that we are scanning a "PMD-entry's worth of PTEs". Looking at it like that, I guess I understand why "scan_pmd" makes sense. Fair enough. > > Best Regards, > Yan, Zi