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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2EEE2C19F2D for ; Fri, 5 Aug 2022 14:41:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240935AbiHEOll (ORCPT ); Fri, 5 Aug 2022 10:41:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34232 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230363AbiHEOlk (ORCPT ); Fri, 5 Aug 2022 10:41:40 -0400 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3627F6151; Fri, 5 Aug 2022 07:41:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1659710499; x=1691246499; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=jEZRMajvp62irH+o7cgsjZocWv3ZqbtMu1G37xj5vFw=; b=CceQ7Xbdwk4FWfHSrIVCYF6ff5Z1hYhHkCpzaNPgJEEI/piT+/ZMbl6P SqtEnwqF/XLS6DQ3RBnwRCJwIdGUugwGkU7n8xeF796z8LoAJjurEcThq 15rFBxPQZvf5maVLgh4FY1DbmBktpfJMvyZdBH+JiovTEl6HTpvD19kT0 2U/8m+ed3yw2aG3hfYISXCWZI3ExlgmdzXPF6wAquOgq+yyTuiqFIq75H +wBzSu3kPgnjyFGUJHTXxCOeXqBY5OYSBaTi1nbjXcL72xz9oAdXI9Glo kSbxurz8IagGvVhOtW7RZ67EkM7dur8WCebtt8tRrjHu8VNQredBnwr7w Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10430"; a="376508901" X-IronPort-AV: E=Sophos;i="5.93,216,1654585200"; d="scan'208";a="376508901" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Aug 2022 07:41:38 -0700 X-IronPort-AV: E=Sophos;i="5.93,216,1654585200"; d="scan'208";a="579518635" Received: from rderber-mobl1.amr.corp.intel.com (HELO [10.212.217.71]) ([10.212.217.71]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Aug 2022 07:41:37 -0700 Message-ID: Date: Fri, 5 Aug 2022 07:41:38 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCHv7 02/14] mm: Add support for unaccepted memory Content-Language: en-US To: Vlastimil Babka , David Hildenbrand , "Kirill A. Shutemov" , Borislav Petkov , Andy Lutomirski , Sean Christopherson , Andrew Morton , Joerg Roedel , Ard Biesheuvel Cc: Andi Kleen , Kuppuswamy Sathyanarayanan , David Rientjes , Tom Lendacky , Thomas Gleixner , Peter Zijlstra , Paolo Bonzini , Ingo Molnar , Dario Faggioli , Mike Rapoport , marcelo.cerri@canonical.com, tim.gardner@canonical.com, khalid.elmously@canonical.com, philip.cox@canonical.com, x86@kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, Mike Rapoport , Mel Gorman References: <20220614120231.48165-1-kirill.shutemov@linux.intel.com> <20220614120231.48165-3-kirill.shutemov@linux.intel.com> <8cf143e7-2b62-1a1e-de84-e3dcc6c027a4@suse.cz> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/5/22 06:38, Vlastimil Babka wrote: >> I'm sure we could optimize for the !unaccepted memory via static keys >> also in this version with some checks at the right places if we find >> this to hurt performance? > It would be great if we would at least somehow hit the necessary code only > when dealing with a >=pageblock size block. The bitmap approach and > accepting everything smaller uprofront actually seems rather compatible. Yet > in the current patch we e.g. check PageUnaccepted(buddy) on every buddy size > while merging. Needing to check PageUnaccepted() during the merge is fallout from moving the acceptance to post_alloc_hook(). I _think_ an earlier version of this did page acceptance under the zone lock, closer to where the page comes off the 2M/4M lists. But, page acceptance is horribly slow, so I asked Kirill to move it out from under the zone lock. Doing it in post_alloc_hook() (after the zone lock is dropped) makes a lot of sense since we do zeroing in there and zeroing is also nice and slow. But, post_alloc_hook() is long after the 2M page has been split and that means that we have to deal with potentially unaccepted pages during merges. I think there are three basic options: 1. This patch: Do acceptance after the zone lock is dropped and deal with mixed-acceptance merges 2. Do acceptance under the zone lock as pages come off the 2M/4M lists, but before the page is split. 3. Pull the page off the 2M/4M lists, drop the zone lock, accept it, then put it back. I'm not sure any of those other options are better.