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 BAB4CC433EF for ; Tue, 5 Jul 2022 13:17:59 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5060C6B0071; Tue, 5 Jul 2022 09:17:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4B5C56B0073; Tue, 5 Jul 2022 09:17:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3A55A6B0074; Tue, 5 Jul 2022 09:17:59 -0400 (EDT) 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 2C8F36B0071 for ; Tue, 5 Jul 2022 09:17:59 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 41725354D8 for ; Tue, 5 Jul 2022 13:17:58 +0000 (UTC) X-FDA: 79653099036.02.94EACD3 Received: from out30-56.freemail.mail.aliyun.com (out30-56.freemail.mail.aliyun.com [115.124.30.56]) by imf15.hostedemail.com (Postfix) with ESMTP id 46C95A0056 for ; Tue, 5 Jul 2022 13:17:54 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046050;MF=guanghuifeng@linux.alibaba.com;NM=1;PH=DS;RN=21;SR=0;TI=SMTPD_---0VISKJA4_1657027069; Received: from 30.225.28.170(mailfrom:guanghuifeng@linux.alibaba.com fp:SMTPD_---0VISKJA4_1657027069) by smtp.aliyun-inc.com; Tue, 05 Jul 2022 21:17:50 +0800 Message-ID: <51f7c840-f892-fa98-632b-4c06b76fb32a@linux.alibaba.com> Date: Tue, 5 Jul 2022 21:17:48 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v4] arm64: mm: fix linear mem mapping access performance degradation To: Mike Rapoport , Will Deacon Cc: Ard Biesheuvel , baolin.wang@linux.alibaba.com, catalin.marinas@arm.com, akpm@linux-foundation.org, david@redhat.com, jianyong.wu@arm.com, james.morse@arm.com, quic_qiancai@quicinc.com, christophe.leroy@csgroup.eu, jonathan@marek.ca, mark.rutland@arm.com, thunder.leizhen@huawei.com, anshuman.khandual@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, geert+renesas@glider.be, linux-mm@kvack.org, yaohongbo@linux.alibaba.com, alikernel-developer@linux.alibaba.com References: <4accaeda-572f-f72d-5067-2d0999e4d00a@linux.alibaba.com> <20220704131516.GC31684@willie-the-truck> <2ae1cae0-ee26-aa59-7ed9-231d67194dce@linux.alibaba.com> <20220704142313.GE31684@willie-the-truck> <6977c692-78ca-5a67-773e-0389c85f2650@linux.alibaba.com> <20220704163815.GA32177@willie-the-truck> <20220705095231.GB552@willie-the-truck> <5d044fdd-a61a-d60f-d294-89e17de37712@linux.alibaba.com> <20220705121115.GB1012@willie-the-truck> From: "guanghui.fgh" In-Reply-To: Content-Type: text/plain; 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cv=none; b=rUU7Mod3uAyuCQ69GZcr9lizAwT7+mJxLKmi2HNqgEjSCYaqJ+qxhO8LzKpM2vHXAplCDv lc+63RMlCNo052qylAmZhCbMz7pTWgydkI10GRmkW0zK7UHXC754Z8QUlpY2Rmyi4cC176 o3fei7UMreMZ0p9Cwknq7iVWybdy8x0= Authentication-Results: imf15.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf15.hostedemail.com: domain of guanghuifeng@linux.alibaba.com designates 115.124.30.56 as permitted sender) smtp.mailfrom=guanghuifeng@linux.alibaba.com X-Stat-Signature: gru45usyc3n7r7dkwa6n5qxiahhrtkxr X-Rspamd-Queue-Id: 46C95A0056 X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1657027074-507643 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: 在 2022/7/5 20:56, Mike Rapoport 写道: > On Tue, Jul 05, 2022 at 01:11:16PM +0100, Will Deacon wrote: >> On Tue, Jul 05, 2022 at 08:07:07PM +0800, guanghui.fgh wrote: >>> >>> 1.The rodata full is harm to the performance and has been disabled in-house. >>> >>> 2.When using crashkernel with rodata non full, the kernel also will use non >>> block/section mapping which cause high d-TLB miss and degrade performance >>> greatly. >>> This patch fix it to use block/section mapping as far as possible. >>> >>> bool can_set_direct_map(void) >>> { >>> return rodata_full || debug_pagealloc_enabled(); >>> } >>> >>> map_mem: >>> if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE)) >>> flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; >>> >>> 3.When rodata full is disabled, crashkernel also need protect(keep >>> arch_kexec_[un]protect_crashkres using). >>> I think crashkernel should't depend on radata full(Maybe other architecture >>> don't support radata full now). >> >> I think this is going round in circles :/ >> >> As a first step, can we please leave the crashkernel mapped unless >> rodata=full? It should be a much simpler patch to write, review and maintain >> and it gives you the performance you want when crashkernel is being used. > > Since we are talking about large systems, what do you think about letting > them set CRASH_ALIGN to PUD_SIZE, then > > unmap(crashkernel); > __create_pgd_mapping(crashkernel, NO_BLOCK_MAPPINGS); > > should be enough to make crash kernel mapped with base pages. > >> Will > Thanks. 1.When kernel boots with crashkernel, the crashkernel parameters format is: 0M-2G:0M,2G-256G:256M,256G-1024G:320M,1024G-:384M which is self-adaption to multiple system. 2.As mentioned above, the crashkernel mem size maybe less than PUD_SIZE(Not multiple time to PUD_SIZE). So, maybe we also need use some non block/section mappings.