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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1535AC48BC4 for ; Wed, 14 Feb 2024 10:43:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 87D258D000E; Wed, 14 Feb 2024 05:43:49 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 806A98D0001; Wed, 14 Feb 2024 05:43:49 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6A7188D000E; Wed, 14 Feb 2024 05:43:49 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 56A0A8D0001 for ; Wed, 14 Feb 2024 05:43:49 -0500 (EST) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 23E43140786 for ; Wed, 14 Feb 2024 10:43:49 +0000 (UTC) X-FDA: 81790073778.13.8A0AD78 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf15.hostedemail.com (Postfix) with ESMTP id 61F8EA0013 for ; Wed, 14 Feb 2024 10:43:47 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=none; spf=pass (imf15.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1707907427; 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=JCGHnetQKMd4PSvQddFAQFFTlIm+A32ALBMJvIVaaM0=; b=xoVIkzhnI3hCRANY5BubS9AaOgTnopfTInYpA3PF4oanSSpa2dpjGjjlaITie9riz+2O2K SI/QuJtpwrmCxhljNHELxjw+0/5R1khIQOp9wJIlFfFixNCGmHYPMAlRTfeVJgCTPcrLKk ynx7JgcoY+mcgweKXqfsDjcHOnhSeww= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1707907427; a=rsa-sha256; cv=none; b=N7A/YwCpH5kBYtvdlRRm7MgB8NMN3NSSDHpOy33dEmSTzNgS7XvGCLgwKCsfyAgN1O5EE5 v3neUKQIZXW5sTyVi7vm72wszIbE6AAP7NRuhPy1YsvvP12vU3s3TMRkCmoRlGxRk9BBkS 3d7KDQJSnDThDtJp7CLeFk9soqcC2LE= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=none; spf=pass (imf15.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com 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 84CA5DA7; Wed, 14 Feb 2024 02:44:27 -0800 (PST) Received: from [10.57.64.120] (unknown [10.57.64.120]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DE4A83F766; Wed, 14 Feb 2024 02:43:43 -0800 (PST) Message-ID: Date: Wed, 14 Feb 2024 10:43:42 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 6/7] mm: truncate: split huge page cache page to a non-zero order if possible. Content-Language: en-GB To: Zi Yan , "Pankaj Raghav (Samsung)" , linux-mm@kvack.org Cc: "Matthew Wilcox (Oracle)" , David Hildenbrand , Yang Shi , Yu Zhao , "Kirill A . Shutemov" , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Roman Gushchin , Zach O'Keefe , Hugh Dickins , Mcgrof Chamberlain , Andrew Morton , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20240213215520.1048625-1-zi.yan@sent.com> <20240213215520.1048625-7-zi.yan@sent.com> From: Ryan Roberts In-Reply-To: <20240213215520.1048625-7-zi.yan@sent.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 61F8EA0013 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 5g3bn4xmfucgg5disdptnx5upuuatk1r X-HE-Tag: 1707907427-27272 X-HE-Meta: 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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 13/02/2024 21:55, Zi Yan wrote: > From: Zi Yan > > To minimize the number of pages after a huge page truncation, we do not > need to split it all the way down to order-0. The huge page has at most > three parts, the part before offset, the part to be truncated, the part > remaining at the end. Find the greatest common divisor of them to > calculate the new page order from it, so we can split the huge > page to this order and keep the remaining pages as large and as few as > possible. > > Signed-off-by: Zi Yan > --- > mm/truncate.c | 21 +++++++++++++++++++-- > 1 file changed, 19 insertions(+), 2 deletions(-) > > diff --git a/mm/truncate.c b/mm/truncate.c > index 725b150e47ac..49ddbbf7a617 100644 > --- a/mm/truncate.c > +++ b/mm/truncate.c > @@ -21,6 +21,7 @@ > #include > #include > #include > +#include > #include "internal.h" > > /* > @@ -210,7 +211,8 @@ int truncate_inode_folio(struct address_space *mapping, struct folio *folio) > bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end) > { > loff_t pos = folio_pos(folio); > - unsigned int offset, length; > + unsigned int offset, length, remaining; > + unsigned int new_order = folio_order(folio); > > if (pos < start) > offset = start - pos; > @@ -221,6 +223,7 @@ bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end) > length = length - offset; > else > length = end + 1 - pos - offset; > + remaining = folio_size(folio) - offset - length; > > folio_wait_writeback(folio); > if (length == folio_size(folio)) { > @@ -235,11 +238,25 @@ bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end) > */ > folio_zero_range(folio, offset, length); > > + /* > + * Use the greatest common divisor of offset, length, and remaining > + * as the smallest page size and compute the new order from it. So we > + * can truncate a subpage as large as possible. Round up gcd to > + * PAGE_SIZE, otherwise ilog2 can give -1 when gcd/PAGE_SIZE is 0. > + */ > + new_order = ilog2(round_up(gcd(gcd(offset, length), remaining), > + PAGE_SIZE) / PAGE_SIZE); Given you have up to 2 regions remaining, isn't it possible that you want a different order for both those regions (or even multiple orders within the same region)? I guess you just choose gcd for simplicity? > + > + /* order-1 THP not supported, downgrade to order-0 */ > + if (new_order == 1) > + new_order = 0; I guess this would need to change if supporting order-1 file folios? > + > + > if (folio_has_private(folio)) > folio_invalidate(folio, offset, length); > if (!folio_test_large(folio)) > return true; > - if (split_folio(folio) == 0) > + if (split_huge_page_to_list_to_order(&folio->page, NULL, new_order) == 0) I know you are discussing removing this patch, but since you created split_folio_to_order() wouldn't that be better here? Thanks, Ryan > return true; > if (folio_test_dirty(folio)) > return false;