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 32E67EB64DD for ; Tue, 4 Jul 2023 23:57:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5FABB2800C7; Tue, 4 Jul 2023 19:57:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5AAF92800B2; Tue, 4 Jul 2023 19:57:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 472572800C7; Tue, 4 Jul 2023 19:57:45 -0400 (EDT) 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 37A762800B2 for ; Tue, 4 Jul 2023 19:57:45 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 14346A03F5 for ; Tue, 4 Jul 2023 23:57:45 +0000 (UTC) X-FDA: 80975594490.01.9FD4F79 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf03.hostedemail.com (Postfix) with ESMTP id 22A0020009 for ; Tue, 4 Jul 2023 23:57:42 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b="Epqs/Hbh"; dmarc=none; spf=none (imf03.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1688515063; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=12jw7f37Y05R+QFxMlhYK7Zaoz60JCyqvKUQKE8Aprs=; b=2CMWqQuRYxo+/mm0hMOJAQFgE5tqYNTqTmIx+oCA50iNs7B3TgT7AkKdMD9ZPnjV00qGJR yOMkIEG5IvffScmLYU4gmqYCqRi9ghrwi91fCbHhvTVTqb51PG4GhQl0yetwAhJAZyCgKP wNAME6AWBw6LBol7S8M4DleFnsbnEbE= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b="Epqs/Hbh"; dmarc=none; spf=none (imf03.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1688515063; a=rsa-sha256; cv=none; b=sZ1aSzEMbHSi7hhDK0JuuoGlh0YlAvMGD7NHeiDYzd+KhvOlKnriHLUGLCw/4vGhogjiXk aZ2NfNbeAGAgMjlxDTVudlYeQQ4xhcSzUwnOZFSWqjS/wmT/bEBDcqm458PUHOyOtvmOkY p2iyDz/J3XE8fycPgYHfOOhsW0k3g2M= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=12jw7f37Y05R+QFxMlhYK7Zaoz60JCyqvKUQKE8Aprs=; b=Epqs/HbhRoft4XM5q4tKqGXcOk 0jFcDZF01KB1zjYQKv3tprKnDYITw7X/XyAc/PgoK/A9BZ3ihs3DLb8XObg0zwQDK1FbGPv772wGN /xryW9aQF7CGjipkbPDIER5mW30SKc+Og96eGXmIXmPUYDT41vo6lWNzei6pDwmT5dkcnuR/MKeg5 qHm+Ske3XlDLBrTexloPScJF48aex2SNsVUbuGhWUHVnY7nNVZ9zR/9CL0+5UpX/rWMCANtBMG72B sO9aRAtmguhssvFIAK3GT/rZCXXbwKQJSGkju+K8UPR6UWB83MyCPo3o9GRc1tES700+9+hfc13Zh ilOVsdTQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qGptd-009ZtG-FJ; Tue, 04 Jul 2023 23:57:25 +0000 Date: Wed, 5 Jul 2023 00:57:25 +0100 From: Matthew Wilcox To: Ryan Roberts Cc: "Yin, Fengwei" , Andrew Morton , "Kirill A. Shutemov" , David Hildenbrand , Yu Zhao , Catalin Marinas , Will Deacon , Anshuman Khandual , Yang Shi , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 4/5] mm: FLEXIBLE_THP for improved performance Message-ID: References: <20230703135330.1865927-1-ryan.roberts@arm.com> <20230703135330.1865927-5-ryan.roberts@arm.com> <6865a59e-9e40-282d-c434-b7c757388b65@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 22A0020009 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: sgfdzq8bru4nwm91jfo4hijcqabf3zxu X-HE-Tag: 1688515062-122161 X-HE-Meta: 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 yQVpuBCk ITSfyL5eAfmj0Sg7ZkI8pI4Vzqivy/RLwXXsIDOB6qZHNCTCW3laJ4eXUph0BrQr5AR5mgZiXkOvJTpyxfjEE/fPNAts62L0TcxUTd+VoVqk2Wb8H0vvnLRBfv2s1YBZB/3AqEvSZ/W9p76h8huXZN+hGQ/K6ZpZ+0prGWoJcoEAyXKQzgusbxdXURg== 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: On Tue, Jul 04, 2023 at 03:20:35PM +0100, Ryan Roberts wrote: > On 04/07/2023 04:45, Yin, Fengwei wrote: > > > > On 7/3/2023 9:53 PM, Ryan Roberts wrote: > >> Introduce FLEXIBLE_THP feature, which allows anonymous memory to be > > THP is for huge page which is 2M size. We are not huge page here. But > > I don't have good name either. > > Is that really true? On arm64 with 16K pages, huge pages are 32M and with 64K > base page, they are 512M. So huge pages already have a variable size. And they > sometimes get PTE-mapped. So can't we just think of this as an extension of the > THP feature? The confusing thing is that we have counters for the number of THP allocated (and number of THP mapped), and for those we always use PMD-size folios. If we must have a config option, then this is ANON_LARGE_FOLIOS. But why do we need a config option? We don't have one for the page cache, and we're better off for it. Yes, it depends on CONFIG_TRANSPARENT_HUGEPAGE today, but that's more of an accidental heritage, and it'd be great to do away with that dependency eventually. Hardware support isn't needed. Large folios benefit us from a software point of view. if we need a chicken bit, we can edit the source code to not create anon folios larger than order 0.