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 2D12EC48BEB for ; Wed, 14 Feb 2024 10:50:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A321F8D0001; Wed, 14 Feb 2024 05:50:26 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9E2576B00A4; Wed, 14 Feb 2024 05:50:26 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8AB748D0001; Wed, 14 Feb 2024 05:50:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 7B2FC6B00A3 for ; Wed, 14 Feb 2024 05:50:26 -0500 (EST) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 4631DA1D10 for ; Wed, 14 Feb 2024 10:50:26 +0000 (UTC) X-FDA: 81790090452.16.E6377B4 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf19.hostedemail.com (Postfix) with ESMTP id A606B1A0011 for ; Wed, 14 Feb 2024 10:50:24 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf19.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1707907824; 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=pUfgK8/3Zvw4KNdYhiVmFgGZlIeUA3hJI1YkO3cDfJg=; b=Hd57Niu04Oe/aQ6gRM3qV2OSVI/swOptNZWrWnzDBfr7jP6Lcny/xuRqQw6h+gaSh0fRVp EWPLtGP7IOjbq0AXBjF7aGlg0pDanVX5bUNXg4fM7ZIOCscSGaq7hqWrayh0vOqMMg9AUk mZCRFHwIJcKiNnbcnwEEaFIvJ6EJ4+0= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf19.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1707907824; a=rsa-sha256; cv=none; b=V2MsNOHX/tT+gtcwCzBZJUm7GbqYUm9d30BG0K/0Fh6sWWu+5TGuJLNMQkX+dmEEToXKuJ f4mGqmHF5md4TEjeD2xWFPAa69GuPJYHRwxNJWKsPyxXowaSQZwtwlU3VfdbzRQJBaVGYL vPh+VREL2+k5riDxw8qNU+XRwm6nxbY= 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 7259D1FB; Wed, 14 Feb 2024 02:51:04 -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 541673F766; Wed, 14 Feb 2024 02:50:20 -0800 (PST) Message-ID: <66d4b27f-85e4-458e-8d66-54f800c5c65f@arm.com> Date: Wed, 14 Feb 2024 10:50:18 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 0/7] Split a folio to any lower order folios Content-Language: en-GB To: Zi Yan , David Hildenbrand Cc: "Pankaj Raghav (Samsung)" , linux-mm@kvack.org, "Matthew Wilcox (Oracle)" , 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> <659e1abb-40d0-42ba-ba0a-8256d7eb1c5a@redhat.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: A606B1A0011 X-Stat-Signature: tthkjoxryn8mih8zmynoc8f651rnxuhq X-HE-Tag: 1707907824-762992 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 22:31, Zi Yan wrote: > On 13 Feb 2024, at 17:21, David Hildenbrand wrote: > >> On 13.02.24 22:55, Zi Yan wrote: >>> From: Zi Yan >>> >>> Hi all, >>> >>> File folio supports any order and multi-size THP is upstreamed[1], so both >>> file and anonymous folios can be >0 order. Currently, split_huge_page() >>> only splits a huge page to order-0 pages, but splitting to orders higher than >>> 0 is going to better utilize large folios. In addition, Large Block >>> Sizes in XFS support would benefit from it[2]. This patchset adds support for >>> splitting a large folio to any lower order folios and uses it during file >>> folio truncate operations. >>> >>> For Patch 6, Hugh did not like my approach to minimize the number of >>> folios for truncate[3]. I would like to get more feedback, especially >>> from FS people, on it to decide whether to keep it or not. >> >> I'm curious, would it make sense to exclude the "more" controversial parts (i.e., patch #6) for now, and focus on the XFS use case only? > > Sure. Patch 6 was there to make use of split_huge_page_to_list_to_order(). > Now we have multi-size THP and XFS use cases, it can be dropped. What are your plans for how to determine when to split THP and to what order? I don't see anything in this series that would split anon THP to non-zero order? We have talked about using hints from user space in the past (e.g. mremap, munmap, madvise, etc). But chrome has a use case where it temporarily mprotects a single (4K) page as part of garbage collection (IIRC). If you eagerly split on that hint, you will have lost the benefits of the large folio when it later mprotects back to the original setting. I guess David will suggest this would be a good use case for the khugepaged-lite machanism we have been talking about. I dunno - it seems wasteful to split then collapse again. Or perhaps you're considering doing something clever in deferred split? > > -- > Best Regards, > Yan, Zi