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 E77A6CDB47E for ; Fri, 13 Oct 2023 08:49:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230207AbjJMIti (ORCPT ); Fri, 13 Oct 2023 04:49:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230334AbjJMIta (ORCPT ); Fri, 13 Oct 2023 04:49:30 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 70D77136 for ; Fri, 13 Oct 2023 01:49:28 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3F714C433C7; Fri, 13 Oct 2023 08:49:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697186967; bh=HgjG8dXJseeEMaKwgvPf4GwIryB+0yn5uNjJ0rz99XA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WjGAhUltjuJA2XNhwyr0qRX/QPcKHGR+xBp7blnN3CuekjNPJ10dK91M1VFr5rrsF f72hv/KgddY+FYgM1hwIMzc7xFAFjz445ykEmp9+VOxwaSoaKkWENedQOn53yRgXU8 Zka5wtoybkbuDL02DBSwi7IyJM/ki5Ole9zKoOngTXaEGBX140BMqYhDtTx0DaIvV/ QCgGQzK7ppL+F+60BNLBXWGDHUJH36P6h+9VfFS9wMINIvdDfxBHplPXaNJ6VijI7g jF02GmDzScVqJzyzOAmfx+stRpltbFk+6aoa7A6Ak2WR1T9n536wb0EY/xPelkej7a Wqop4NhhKsy/Q== Date: Fri, 13 Oct 2023 11:48:27 +0300 From: Mike Rapoport To: Yajun Deng Cc: David Hildenbrand , akpm@linux-foundation.org, mike.kravetz@oracle.com, muchun.song@linux.dev, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/2] mm: Init page count in reserve_bootmem_region when MEMINIT_EARLY Message-ID: <20231013084827.GT3303@kernel.org> References: <20230928083302.386202-1-yajun.deng@linux.dev> <20230928083302.386202-3-yajun.deng@linux.dev> <20230929083018.GU3303@kernel.org> <2f8c4741-5c7f-272d-9cef-9fda9fbc7ca6@linux.dev> <5382bf2d-5aa0-1498-8169-3248be4b5af3@linux.dev> <38cd0cb9-efe9-b98a-2768-ccb48da8b812@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <38cd0cb9-efe9-b98a-2768-ccb48da8b812@linux.dev> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 12, 2023 at 05:53:22PM +0800, Yajun Deng wrote: > > On 2023/10/12 17:23, David Hildenbrand wrote: > > On 10.10.23 04:31, Yajun Deng wrote: > > > > > > On 2023/10/8 16:57, Yajun Deng wrote: > > > > > > > > > > That looks wrong. if the page count would by pure luck be 0 > > > > > already for hotplugged memory, you wouldn't clear the reserved > > > > > flag. > > > > > > > > > > These changes make me a bit nervous. > > > > > > > > Is 'if (page_count(page) || PageReserved(page))' be safer? Or do I > > > > need to do something else? > > > > > > > > > > How about the following if statement? But it needs to add more patch > > > like v1 ([PATCH 2/4] mm: Introduce MEMINIT_LATE context). > > > > > > It'll be safer, but more complex. Please comment... > > > > > >     if (context != MEMINIT_EARLY || (page_count(page) || > > > PageReserved(page)) { > > > > > > > Ideally we could make initialization only depend on the context, and not > > check for count or the reserved flag. > > > > This link is v1, > https://lore.kernel.org/all/20230922070923.355656-1-yajun.deng@linux.dev/ > > If we could make initialization only depend on the context, I'll modify it > based on v1. Although ~20% improvement looks impressive, this is only optimization of a fraction of the boot time, and realistically, how much 56 msec saves from the total boot time when you boot a machine with 190G of RAM? I still think the improvement does not justify the churn, added complexity and special casing of different code paths of initialization of struct pages. > @Mike,  By the way,  this code will cost more time: > >                 if (context == MEMINIT_HOTPLUG) >                         flags = INIT_PAGE_COUNT | INIT_PAGE_RESERVED; >                 __init_single_page(page, pfn, zone, nid, flags); > > > [    0.014999] On node 0, zone DMA32: 31679 pages in unavailable ranges > [    0.311560] ACPI: PM-Timer IO Port: 0x508 > > > This code will cost less time: > >                 __init_single_page(page, pfn, zone, nid, 0); >                 if (context == MEMINIT_HOTPLUG) { >                         init_page_count(page); >                         __SetPageReserved(page); > > [    0.014299] On node 0, zone DMA32: 31679 pages in unavailable ranges > [    0.250223] ACPI: PM-Timer IO Port: 0x508 > -- Sincerely yours, Mike.