From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6017ECA0FF9 for ; Sat, 30 Aug 2025 02:15:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8DD626B0022; Fri, 29 Aug 2025 22:15:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8B4A96B0023; Fri, 29 Aug 2025 22:15:12 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7F19B6B0026; Fri, 29 Aug 2025 22:15:12 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 6D9F36B0022 for ; Fri, 29 Aug 2025 22:15:12 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id E785D85A03 for ; Sat, 30 Aug 2025 02:15:11 +0000 (UTC) X-FDA: 83831806422.01.7428D34 Received: from mail-wm1-f51.google.com (mail-wm1-f51.google.com [209.85.128.51]) by imf12.hostedemail.com (Postfix) with ESMTP id EA72D40002 for ; Sat, 30 Aug 2025 02:15:09 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=QUW3s+Uf; spf=pass (imf12.hostedemail.com: domain of richard.weiyang@gmail.com designates 209.85.128.51 as permitted sender) smtp.mailfrom=richard.weiyang@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1756520110; h=from:from:sender:reply-to: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=IbW8yA03bKLcMTZU8xuLw+CaeqZfBLjJOer3Kg/k+e0=; b=VYVNABvNMHpPC54FjvpgkGEK4giiiniamxQrwo2Mhs47wfH4xVSY0nD7N3eCPRqwEQKjIw IS3fVKJSR502PgOtLflibrfF+fwoD6ph6EuP0zcGGWGhPk1V1O0mQdYPiCHQ4TQBjqls4f wrBdRtdSuppAyiLDkyasPpNtBnJPnBo= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=QUW3s+Uf; spf=pass (imf12.hostedemail.com: domain of richard.weiyang@gmail.com designates 209.85.128.51 as permitted sender) smtp.mailfrom=richard.weiyang@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1756520110; a=rsa-sha256; cv=none; b=26MS9wimiWLQzEdRzVgqhzJD3XJyP3MtMhJ1TbVvAZoLjVqNstvY1v4Vd2b3XMFp16Lh9t /xzWddtTC78vxqCPPthLt1cfmakqdGtsTOPa0apx/bjvpN49tjB+eekmW2ynbTKl6A/dQn YCnE7z73yTsQuTEj5gXi5GFljl9LCQM= Received: by mail-wm1-f51.google.com with SMTP id 5b1f17b1804b1-45b77f59bd8so13650115e9.0 for ; Fri, 29 Aug 2025 19:15:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1756520108; x=1757124908; darn=kvack.org; h=user-agent:in-reply-to:content-disposition:mime-version:references :reply-to:message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=IbW8yA03bKLcMTZU8xuLw+CaeqZfBLjJOer3Kg/k+e0=; b=QUW3s+Uf8VO0VWjy+kA5jTD7maze27nSltYCarQZNxGfeUn8Lm7GPoRqlXW2ij3Hr6 v5nWpU4kLZ+RSyxZQHVt93vf8ZfTJLvhDPlBT8s9guOllQCcpAHOFvhrKGZI47V0Vm1X RMjXzUHWDzX0SaJp5VAE4IIbf8OlEuXT+32VKk+PZ2xv2ZSiELgclm8JLLsOYfK+G3mQ /tEhTDGg57bENXwi+coyoHkGT6BBB1G1Viezix9lr1TsNtL5SEGhlnFy/YFJWocMsd8+ tSgIS1SQJx/vFotfaAXiXntgJUfNhyWYfb2+ndMvll/1QuT20nh8iZB8C+cpdJebMVeX exkQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1756520108; x=1757124908; h=user-agent:in-reply-to:content-disposition:mime-version:references :reply-to:message-id:subject:cc:to:from:date:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=IbW8yA03bKLcMTZU8xuLw+CaeqZfBLjJOer3Kg/k+e0=; b=CzNEVmqvad6N5mhGZWIFQ5LoEvEnq/7M7IHItxczZD81x0f4c4NVhDlKN3lZZEkn+m y6D+fEFksQD5+7AVrWgWHBgJI2OpCuO+qAah2TIMDffYCXxrC4Wo9DJRU0ZWwr9pLbI2 UP0obSbAkCnyLZo760OUkQ/QwXOed/8gNZB2hhxj2kNoXb/i0LokTzLXqlCgsJCaaEnD qqKIMYK0f0aupsi4c8jP210go6WnMrfwd1Ar4bcPGIBzA6544dEOyz/dQClGmsd6l62O wGXHXhC/VDPPCl2cc7TlCh/PqPTcu3fdztuk5gh/Cy63h4HjIAvtweORcvIidL+jkZP5 e2HA== X-Forwarded-Encrypted: i=1; AJvYcCX3vG+gYqq/ueCrdiaaLsHKQJpGwm0ShdYryT+xG1Fs1dOi8p+7Y4hXvJNV6DsIwvEAqSjNXQo2dA==@kvack.org X-Gm-Message-State: AOJu0YzQRvRx8rYvg6kkWbCt/hLNmq0DPSzNhg1hw4qMy/XxSziW+Sek TaPqspn0BoG1Ay41NMplDTnkELzbbp2zKBTNP+LcAib2ykvPhn5gPOiQ X-Gm-Gg: ASbGnctbr+3e7DMPbuxSzvpJzHfkuETyZh9MV76pvvMXOJotuLMwHJDrGOjqAtHZjaQ UirqKn0n75hsMh7BpNSqKUYrG2sZqk69WjiYje2WsnAZnI8hKCfzF5PWmNE8pkRrXiCUON/DZwL 4mP4GK+1GOAQTT0TiN/I8BC7K8SG0RrtkkBQ4BUf+865A+JluwskxKkaTa6PS+8HV6u+LjdnihZ I5vF85P/27h/yCXVDNcDloYDbA9MCCJs/btSyfSO/guejgk2DWxTw8E/SkJ6/ykdCGxZz2cW+sm 5yF0hYi0S1F3TKkSUeXXIstITWUkw2azARhugTxr3hsqVdrHdam1t24lFMNRPmY268AiJpwv1VY rg2D5Kz1dBnO8qwzfOKGQBKLRiw== X-Google-Smtp-Source: AGHT+IEZ2xFlU2ogeDVnDCaG1GcpwFQhH4uXS3OA3m8V+IApCgexhyPxGxyko+OJwospCM8rYhx31w== X-Received: by 2002:a5d:64ee:0:b0:3d1:abf7:e1d3 with SMTP id ffacd0b85a97d-3d1b1aef463mr566337f8f.20.1756520108168; Fri, 29 Aug 2025 19:15:08 -0700 (PDT) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3cf33fb9cebsm5308064f8f.46.2025.08.29.19.15.07 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Fri, 29 Aug 2025 19:15:07 -0700 (PDT) Date: Sat, 30 Aug 2025 02:15:06 +0000 From: Wei Yang To: Zi Yan Cc: Wei Yang , akpm@linux-foundation.org, linux-mm@kvack.org, Johannes Weiner , Vlastimil Babka , David Hildenbrand Subject: Re: [PATCH] mm/page_alloc: find_large_buddy() from start_pfn aligned order Message-ID: <20250830021506.q34jktg64h74hux7@master> Reply-To: Wei Yang References: <20250828091618.7869-1-richard.weiyang@gmail.com> <489045AD-70D6-4167-843D-50A8DD19870B@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <489045AD-70D6-4167-843D-50A8DD19870B@nvidia.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Stat-Signature: qo8yj5mqh1e8jqybfix3mcmfwu1pyoq8 X-Rspam-User: X-Rspamd-Queue-Id: EA72D40002 X-Rspamd-Server: rspam01 X-HE-Tag: 1756520109-783741 X-HE-Meta: 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 jEINSwHC 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 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 Thu, Aug 28, 2025 at 11:02:33PM -0400, Zi Yan wrote: [...] > >BTW, I also notice that when start_pfn is an order-0 PageBuddy, the >"if (pfn + (1 << buddy_order(page)) > start_pfn)" check below would be true >even if there is no buddy straddles start_pfn, although "return pfn" >gives the same results as "return start_pfn" (no straddle). The original >code before the addition of find_large_buddy() (commit fd919a85cd55 ("mm: >page_isolation: prepare for hygienic freelists")) checks start_pfn == pfn >before the straddle check, so the correct code should check start_pfn == pfn >and return early. But since current code is functionally equivalent. >Maybe adding a comment about it would be sufficient. Something like: > >When the found buddy order is 0, the check would give false positive, >but the returned result is still correct, since pfn is the same as start_pfn. Hm... found another thing. In __move_freepages_block_isolate(), when checking "We're the starting block of a large buddy", variable "page" may not be the large buddy page we found from find_large_buddy(). Since prep_move_freepages_block() set start_pfn to pageblock_start_pfn(page_to_pfn(page)), which may be different. -- Wei Yang Help you, Help me