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 784A6C43334 for ; Mon, 4 Jul 2022 11:14:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D8F0C6B0072; Mon, 4 Jul 2022 07:14:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D3F326B0073; Mon, 4 Jul 2022 07:14:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C54DF6B0074; Mon, 4 Jul 2022 07:14:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id B73D66B0072 for ; Mon, 4 Jul 2022 07:14:13 -0400 (EDT) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id 8A730606C1 for ; Mon, 4 Jul 2022 11:14:13 +0000 (UTC) X-FDA: 79649158386.12.B0CB44B Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf07.hostedemail.com (Postfix) with ESMTP id 0C2C040004 for ; Mon, 4 Jul 2022 11:14:12 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 66E5FB80E88; Mon, 4 Jul 2022 11:14:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 658D0C341CA; Mon, 4 Jul 2022 11:14:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1656933250; bh=klOYLUi5vKbP7lLXPlg3VywRiC6zi5lv+GFCDUacxQ4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nQ9jXCF2NYWAAv8fe8XVgTNnCLyXBOTaZWTiQOC4cwuzd8Q4vJ+UD0H1EWlmZn+Ck VZ1wdXcXsKfGvIK1NX5keAaCcxU4FLZpumoeUJBb7WH6YrLlnHl8EY1mpQyF9ymn1h M/OSILsEjYJy8wuNBLxNqxKwyKPchvfsX6Ig/fkSgAZlOP05GKWJ+jnYUcq1L5s3tq cRBMp667H+23Pqt4EEsMI/BauNcg8EXzDUFTz+CPFQu/7wCimx6HCDkxqM68WbMTQd mSCMXzb3LHG8BBlOVcU9ctEl4BmOZdAfsYOehzZvl1RbLv+oG4GkSQo6RdGsMCzm6L sm68TYRAf8/Dw== Date: Mon, 4 Jul 2022 12:14:02 +0100 From: Will Deacon To: "guanghui.fgh" Cc: 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, rppt@kernel.org, geert+renesas@glider.be, ardb@kernel.org, linux-mm@kvack.org, yaohongbo@linux.alibaba.com, alikernel-developer@linux.alibaba.com Subject: Re: [PATCH v4] arm64: mm: fix linear mem mapping access performance degradation Message-ID: <20220704111402.GA31553@willie-the-truck> References: <1656777473-73887-1-git-send-email-guanghuifeng@linux.alibaba.com> <20220704103523.GC31437@willie-the-truck> <73f0c53b-fd17-c5e9-3773-1d71e564eb50@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <73f0c53b-fd17-c5e9-3773-1d71e564eb50@linux.alibaba.com> User-Agent: Mutt/1.10.1 (2018-07-13) ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656933253; a=rsa-sha256; cv=none; b=AUcpH/GESQpbHBRoR38L6+diNKbMRcwcYNfAANbG0XF48gn7GXxB/lPaB+09UnJSiJtIHh AjSyp7zXbOaIHGWoHeYtiMZAfInZ16k07qLlmf3e4N12pfov1TpqI3njaPMCdVljweZoev 3Sy9bNxCIf06cCcVG0Xba79g2dcAW0s= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=nQ9jXCF2; spf=pass (imf07.hostedemail.com: domain of will@kernel.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=will@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656933253; 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=v5zvp+zpATvtqQPZoL0wa8fxMcI2vNrrG5aommaqOkw=; b=lN3uz54YmnSTt7IQDoCJ8PJhNcVrT2kdhVjUhy0AjidxmC0wOt+YxTxNXkyRwg+K2y3nL/ 2LRtXOu+BSKdiFiWsnh0gd7xQKMdjzLVVb0SHDLlSpsqBkMh7L/kYyl4FaTNbe2Q+iOowo ZxLWtknCnEMQCNl7VsrUi57d2hlxRiY= X-Stat-Signature: 35pprofcbkfp95x7d7uaj34ha9g1z8j9 X-Rspamd-Queue-Id: 0C2C040004 Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=nQ9jXCF2; spf=pass (imf07.hostedemail.com: domain of will@kernel.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=will@kernel.org; dmarc=pass (policy=none) header.from=kernel.org X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1656933252-240129 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 Mon, Jul 04, 2022 at 06:58:20PM +0800, guanghui.fgh wrote: > > > 在 2022/7/4 18:35, Will Deacon 写道: > > On Sat, Jul 02, 2022 at 11:57:53PM +0800, Guanghui Feng wrote: > > > The arm64 can build 2M/1G block/sectiion mapping. When using DMA/DMA32 zone > > > (enable crashkernel, disable rodata full, disable kfence), the mem_map will > > > use non block/section mapping(for crashkernel requires to shrink the region > > > in page granularity). But it will degrade performance when doing larging > > > continuous mem access in kernel(memcpy/memmove, etc). > > > > Hmm. It seems a bit silly to me that we take special care to unmap the > > crashkernel from the linear map even when can_set_direct_map() is false, as > > we won't be protecting the main kernel at all! > > > > Why don't we just leave the crashkernel mapped if !can_set_direct_map() > > and then this problem just goes away? > > > > Will > > This question had been asked lask week. Sorry, I didn't spot that. Please could you link me to the conversation, as I'm still unable to find it in my inbox? > 1.Quoted messages from arch/arm64/mm/init.c > > "Memory reservation for crash kernel either done early or deferred > depending on DMA memory zones configs (ZONE_DMA) -- > > In absence of ZONE_DMA configs arm64_dma_phys_limit initialized > here instead of max_zone_phys(). This lets early reservation of > crash kernel memory which has a dependency on arm64_dma_phys_limit. > Reserving memory early for crash kernel allows linear creation of block > mappings (greater than page-granularity) for all the memory bank rangs. > In this scheme a comparatively quicker boot is observed. > > If ZONE_DMA configs are defined, crash kernel memory reservation > is delayed until DMA zone memory range size initialization performed in > zone_sizes_init(). The defer is necessary to steer clear of DMA zone > memory range to avoid overlap allocation. > > [[[ > So crash kernel memory boundaries are not known when mapping all bank memory > ranges, which otherwise means not possible to exclude crash kernel range > from creating block mappings so page-granularity mappings are created for > the entire memory range. > ]]]" > > Namely, the init order: memblock init--->linear mem mapping(4k mapping for > crashkernel, requirinig page-granularity changing))--->zone dma > limit--->reserve crashkernel. > So when enable ZONE DMA and using crashkernel, the mem mapping using 4k > mapping. Yes, I understand that is how things work today but I'm saying that we may as well leave the crashkernel mapped (at block granularity) if !can_set_direct_map() and then I think your patch becomes a lot simpler. Will