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 394F5CCA47F for ; Tue, 5 Jul 2022 13:49:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231528AbiGENtD (ORCPT ); Tue, 5 Jul 2022 09:49:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38214 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229995AbiGENsk (ORCPT ); Tue, 5 Jul 2022 09:48:40 -0400 Received: from out199-16.us.a.mail.aliyun.com (out199-16.us.a.mail.aliyun.com [47.90.199.16]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 59C7B21832 for ; Tue, 5 Jul 2022 06:17:56 -0700 (PDT) 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; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.