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 E4AF9C41513 for ; Mon, 16 Oct 2023 08:32:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7B82E8D004F; Mon, 16 Oct 2023 04:32:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 767E28D0001; Mon, 16 Oct 2023 04:32:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 630278D004F; Mon, 16 Oct 2023 04:32:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 4DB438D0001 for ; Mon, 16 Oct 2023 04:32:21 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 1B7C11A0A82 for ; Mon, 16 Oct 2023 08:32:21 +0000 (UTC) X-FDA: 81350657682.02.56A6738 Received: from out-201.mta1.migadu.com (out-201.mta1.migadu.com [95.215.58.201]) by imf01.hostedemail.com (Postfix) with ESMTP id 9758D4000C for ; Mon, 16 Oct 2023 08:32:17 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="Fe/+LI5G"; spf=pass (imf01.hostedemail.com: domain of yajun.deng@linux.dev designates 95.215.58.201 as permitted sender) smtp.mailfrom=yajun.deng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1697445139; 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:dkim-signature; bh=I0xqGBUsZ/HBTfDe2nkPsA9OvD0BWF+V8yLFAzPf5d0=; b=dVlkv/ni2uenaytHXJJ0VVT9sQbQM5JY8TtHV+74oJqskl/HBeLeR4IXgOLJjmXGHmYABQ xWzR3fS8jR0FEHdP1+lycNgtDpiE+4Iw+1D2tIID4JOTXK5KH/O5sz3lHtsYEX9NEpEtxg HvdOXRE6PXRne7ipJIm14qiQ5qmGceQ= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="Fe/+LI5G"; spf=pass (imf01.hostedemail.com: domain of yajun.deng@linux.dev designates 95.215.58.201 as permitted sender) smtp.mailfrom=yajun.deng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1697445139; a=rsa-sha256; cv=none; b=8CdzuGTknycnpRfNN+26M3ajUjjR+vWcRJ3IoNHhP5XXrhi/x0qPzNQWqwoHt3SxxVVozd YNHgnFJB/76CixDh3ZhHLwf5TsZPASp2xvKNzy1r0VYrrDKZ/OlTSC6oRaTUNq93PTrILH JDIbNCTGwJt1+njILkfsDAi/NVcjoOc= Message-ID: <0d890048-be58-5050-02fa-21768059aa0d@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1697445135; h=from:from: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=I0xqGBUsZ/HBTfDe2nkPsA9OvD0BWF+V8yLFAzPf5d0=; b=Fe/+LI5G5jWlF6+mf+kpT9E4n+gew/4T0Gu91oztj6ugfWRZ7ujpgTUux5g6R8JOWCs+LH 1zh15ofkdvLsX0yKor2U6QSgjpGY1zcTe+DGOqNg2DIuWk/jX96z+8ifqL51jhMd8BfCIZ 6/FBxgXSn8wL4KOxD88V8GriZ8OgM1w= Date: Mon, 16 Oct 2023 16:32:07 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v4 2/2] mm: Init page count in reserve_bootmem_region when MEMINIT_EARLY Content-Language: en-US To: David Hildenbrand , Mike Rapoport Cc: akpm@linux-foundation.org, mike.kravetz@oracle.com, muchun.song@linux.dev, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.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> <20231013084827.GT3303@kernel.org> <1c91dd62-886d-bb05-8aee-22191a8a2d8e@linux.dev> <20231016063357.GU3303@kernel.org> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yajun Deng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 9758D4000C X-Rspam-User: X-Stat-Signature: mznity88zr95rwk5tdshnyo6hfkgp3wj X-Rspamd-Server: rspam01 X-HE-Tag: 1697445137-585556 X-HE-Meta: U2FsdGVkX1//dgUuqzKCAd7e7AAOYRnEkKV0TPx77GGXVIlfo7eEJhIHShA44Yo6X2fdcWEJPBncgc/FcBdJa0TMGeomVzpBBiQY8IQVPpZn36dz+yVhBt/DPYsbZ1n0NOjxzZw+OrQAyi2J6SPzHD1GBSS0U8BvR1qzBOeytwUmleN76O7EP7pNSdVKgqq2XCvTIzw1xG2twmQRorEPpYAFJpHI+vMgMN7OaXcCAxGYOibS8aOPeYEWZZwXomMQJ7D+EZElZS1asbVeLTuHsiDw5+6ZKNbWI50N/gTdQK3BOKU/K66VhiaLzJLqNaJgT9OCOyUhwwlkwyap74R5opNl8K8oa3FZEMVx1WZmQp/E/6O9QmlehGBFPOqD8XTeTQ3BwOHVMclTO7CWPMNMpQ/U/SezeFBl0pgc5kxYu2oJ+6OGiz/CoWlryzBa6I40bz7urYygylJiuA+SavOxrcoiNYBs4+OCqAL2iGr1tXs//T6NJ6tImafrh0qm7pl4BlYChcSIlpiAjPHn5PNY/yju45kqvMWuIbzIlNoEnBOXweHgqLH4xMg9tAooLxvng1UzS2FGdNEatOj9nLyIKxNUKaWurcrBjbscZa+w0sK0LkamVXUsTKq7stJf9goowShv037J4PIJzfD7jUDbI/C6PazmzZ2W/jaQUV13aQe35WP09zfeWiXj8pgmQLHKJOldqsv/WtOGodtooNerRwu3qzNHFK4v74a7ZnI7WzngIWtpnpDWMxR+knFVJYEn3dfqqW9AGQw+K06MoIVtmvAeYk6KZI/2aXjO6e9gBiWqgcTjn0O18cZAUdsyhZirgocWp6vr0ExG58bdGV/7c6JWYuP2XzdXL/mEdQ6YWQJY/1tG+XVeCTMN3cXqfBZ9lCs0ghnAWj7w6zRPAXziywwbxMdTkEEJluxtiBxElmc4n6iWep0H+QFnrQQMAR/QQ8YbnwMquukrdvUIe2C 7gTAnG2Y 0SAPNNn7N3svKbGFbACZDOj4tZ2LTEb7U27e12u/PF0dqetfnJuxAPkjN1lI0PGr9wG++DFNrdiwN4yZXsh0hbaNqVtuU44oG0Tc9tmtl07ai4e8OJGKnP+2xscu5I/QVOQ2mYy4f2ekryVvtW+Y/Rwykr8XV9Wb3+0teDYQaJJheZDi780bfSwBJKw2Qd0YABom9 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 2023/10/16 16:16, David Hildenbrand wrote: > On 16.10.23 10:10, Yajun Deng wrote: >> >> On 2023/10/16 14:33, Mike Rapoport wrote: >>> On Fri, Oct 13, 2023 at 05:29:19PM +0800, Yajun Deng wrote: >>>> On 2023/10/13 16:48, Mike Rapoport wrote: >>>>> 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? >>>> There are a lot of factors that can affect the total boot time. 56 >>>> msec >>>> saves may be insignificant. >>>> >>>> But if we look at the boot log, we'll see there's a significant >>>> time jump. >>>> >>>> before: >>>> >>>> [    0.250334] ACPI: PM-Timer IO Port: 0x508 >>>> [    0.618994] Memory: 173413056K/199884452K available (18440K >>>> kernel code, >>>> >>>> after: >>>> >>>> [    0.260229] software IO TLB: area num 32. >>>> [    0.563497] Memory: 173413056K/199884452K available (18440K >>>> kernel code, >>>> Memory: >>>> Memory initialization is time consuming in the boot log. >>> You just confirmed that 56 msec is insignificant and then you send >>> again >>> the improvement of ~60 msec in memory initialization. >>> >>> What does this improvement gain in percentage of total boot time? >> >> >> before: >> >> [   10.692708] Run /init as init process >> >> >> after: >> >> [   10.666290] Run /init as init process >> >> >> About 0.25%. The total boot time is variable, depending on how many >> drivers need to be initialized. >> >> >>>>> I still think the improvement does not justify the churn, added >>>>> complexity >>>>> and special casing of different code paths of initialization of >>>>> struct pages. >>>> >>>> Because there is a loop, if the order is MAX_ORDER, the loop will >>>> run 1024 >>>> times. The following 'if' would be safer: >>>> >>>> 'if (context != MEMINIT_EARLY || (page_count(page) || >> >>>> PageReserved(page)) >>>> {' >>> No, it will not. >>> >>> As the matter of fact any condition here won't be 'safer' because it >>> makes >>> the code more complex and less maintainable. >>> Any future change in __free_pages_core() or one of it's callers will >>> have >>> to reason what will happen with that condition after the change. >> >> >> To avoid introducing MEMINIT_LATE context and make code simpler. This >> might be a better option. >> >> if (page_count(page) || PageReserved(page)) > > I'll have to side with Mike here; this change might not be worth it. > Okay, I got it. Thanks!