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 5CE1CE7719D for ; Sun, 12 Jan 2025 08:55:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 223A36B0092; Sun, 12 Jan 2025 03:55:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1D3CE6B0095; Sun, 12 Jan 2025 03:55:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 09BBE6B0096; Sun, 12 Jan 2025 03:55:17 -0500 (EST) 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 E03186B0092 for ; Sun, 12 Jan 2025 03:55:16 -0500 (EST) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 665F11C6A61 for ; Sun, 12 Jan 2025 08:55:16 +0000 (UTC) X-FDA: 82998190632.11.4388101 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf21.hostedemail.com (Postfix) with ESMTP id B54C81C0004 for ; Sun, 12 Jan 2025 08:55:14 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="bt//TFsj"; spf=pass (imf21.hostedemail.com: domain of rppt@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1736672114; 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=R0zwgCtXOX9INcLxT8PUdhpiuzZmyEDq1CB3lorjDO8=; b=265p8JahckoZ6dvGkxU/iA+7mQ7jetKqjCiWrha8QJvOmZhI6C1+iw68WdnZktIblKPZA6 qRrv+mRwRn1mFAkAMr3xT6nvLsWEJhknV9MWzIxXtwsmqLLbZwd1qciFhEPxSY6GIMDX6k DnH+NKaB8wCJmnSL2sEr/OT3nReIGcM= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1736672114; a=rsa-sha256; cv=none; b=R0iNJ1uSRHk3sVtM+iWTOlt2/9ESKVy5wpIaoUSzyYjBOeH/fHleZSak/ARkX2cAKttdex AxsMK7K0/nNLZVOaFxS/1np5Z5L9A1Ie2D+NxV1AuMUZmftzuDEu8bF3Z04bB3XFHIjJtg IZgDvDHAAuVM/NyiIYnshrnJra2AqEM= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="bt//TFsj"; spf=pass (imf21.hostedemail.com: domain of rppt@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 7D03C5C2CB5; Sun, 12 Jan 2025 08:54:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78674C4CEDF; Sun, 12 Jan 2025 08:54:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736672109; bh=2OdLtNhpOzwVLBuyjT4Pmrh9g+J++anxIOyBzX8oFRo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bt//TFsjp7oBP/+mYKotPM1CCH/pvCViP9lReiFZD2VikywkhE1q0XvAzRMYgR9w/ rDXqF5aM9MujwGkgmdrwVN+U9S/HNKSeUhH0oeUj1JklV0TXx4lQhSwaKnFu9xce32 ftWG7NtXr9D1Marf2RroYue+KEiHc08VUhcxsxtgtvH/1RuSspxTlk/8FfWRwTUUWL GQrOHNuzVf53wyl/rIxgHT4G9jfVuY7AOydTBH62p6BSjVcKmEwo1PW/k1dMtwfkJE pWwQqokKV7JcLsi4Ix+zyeqNEodjirjOo+JMvLDH6LUhiX+SLLVYTId1lNsII6yjXH ekVDGfSuma34Q== Date: Sun, 12 Jan 2025 10:54:46 +0200 From: Mike Rapoport To: "Kirill A. Shutemov" Cc: Andrew Morton , Andy Lutomirski , Anton Ivanov , Borislav Petkov , Brendan Higgins , Daniel Gomez , Daniel Thompson , Dave Hansen , David Gow , Douglas Anderson , Ingo Molnar , Jason Wessel , Jiri Kosina , Joe Lawrence , Johannes Berg , Josh Poimboeuf , "Kirill A. Shutemov" , Luis Chamberlain , Mark Rutland , Masami Hiramatsu , Miroslav Benes , "H. Peter Anvin" , Peter Zijlstra , Petr Mladek , Petr Pavlu , Rae Moar , Richard Weinberger , Sami Tolvanen , Shuah Khan , Song Liu , Steven Rostedt , Thomas Gleixner , kgdb-bugreport@lists.sourceforge.net, kunit-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-um@lists.infradead.org, live-patching@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH 3/8] x86/mm/pat: Restore large pages after fragmentation Message-ID: References: <20241227072825.1288491-1-rppt@kernel.org> <20241227072825.1288491-4-rppt@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: B54C81C0004 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 51xgbw89jnnnu4ho1buypteiox7i88md X-HE-Tag: 1736672114-130841 X-HE-Meta: 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 t/VroTIu JlpJCMzvjgRJ7NhuXuWgSK+SqG/T1CzpIIQHZh2v/cGYAHjG1wgcZeWOC/4CYjYyYex+6hI+0kJYwrWOdd6HUwpe3vdkqJktVgAK0MFHaY5RMGV6bZAopYgSHMe8K5hO/OWz70ydEgI5WcKQdWp0ZLFqKtGExnTilFDeC6RVwygA/ci4psCpt7a+pKpQxOJYszSyYOlqT5pRtiS1g0in/wk2Xi9cmHrzcGIeE7xpVCiiCNJA3qji/MTdoHgqIsl+X34SF5S3jssiGXk3qj1V+pZGHHXU8qaKnfMgva1RFNsnYw9n8FTNoUQTx3dU1HYkcY5ejgza3do3qIMI= 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: Hi Kirill, On Fri, Jan 10, 2025 at 12:36:59PM +0200, Kirill A. Shutemov wrote: > On Fri, Dec 27, 2024 at 09:28:20AM +0200, Mike Rapoport wrote: > > From: "Kirill A. Shutemov" > > > > Change of attributes of the pages may lead to fragmentation of direct > > mapping over time and performance degradation as result. > > > > With current code it's one way road: kernel tries to avoid splitting > > large pages, but it doesn't restore them back even if page attributes > > got compatible again. > > > > Any change to the mapping may potentially allow to restore large page. > > > > Hook up into cpa_flush() path to check if there's any pages to be > > recovered in PUD_SIZE range around pages we've just touched. > > > > CPUs don't like[1] to have to have TLB entries of different size for the > > same memory, but looks like it's okay as long as these entries have > > matching attributes[2]. Therefore it's critical to flush TLB before any > > following changes to the mapping. > > > > Note that we already allow for multiple TLB entries of different sizes > > for the same memory now in split_large_page() path. It's not a new > > situation. > > > > set_memory_4k() provides a way to use 4k pages on purpose. Kernel must > > not remap such pages as large. Re-use one of software PTE bits to > > indicate such pages. > > > > [1] See Erratum 383 of AMD Family 10h Processors > > [2] https://lore.kernel.org/linux-mm/1da1b025-cabc-6f04-bde5-e50830d1ecf0@amd.com/ > > > > [rppt@kernel.org: > > * s/restore/collapse/ > > * update formatting per peterz > > * use 'struct ptdesc' instead of 'struct page' for list of page tables to > > be freed > > * try to collapse PMD first and if it succeeds move on to PUD as peterz > > suggested > > * flush TLB twice: for changes done in the original CPA call and after > > collapsing of large pages > > ] > > > > Link: https://lore.kernel.org/all/20200416213229.19174-1-kirill.shutemov@linux.intel.com > > Signed-off-by: Kirill A. Shutemov > > Co-developed-by: Mike Rapoport (Microsoft) > > Signed-off-by: Mike Rapoport (Microsoft) > > When I originally attempted this, the patch was dropped because of > performance regressions. Was it addressed somehow? I didn't realize the patch was dropped because of performance regressions, so I didn't address it. Do you remember where did the regressions show up? > -- > Kiryl Shutsemau / Kirill A. Shutemov > -- Sincerely yours, Mike.