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 X-Spam-Level: X-Spam-Status: No, score=-7.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8F388C43461 for ; Thu, 3 Sep 2020 15:19:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 61AB720786 for ; Thu, 3 Sep 2020 15:19:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729122AbgICPTt (ORCPT ); Thu, 3 Sep 2020 11:19:49 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:44362 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728513AbgICL1B (ORCPT ); Thu, 3 Sep 2020 07:27:01 -0400 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 4F8BB9C923A5A99C2CA7; Thu, 3 Sep 2020 19:26:39 +0800 (CST) Received: from [127.0.0.1] (10.174.176.220) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.487.0; Thu, 3 Sep 2020 19:26:28 +0800 Subject: Re: [PATCH v11 3/5] arm64: kdump: reimplement crashkernel=X To: Catalin Marinas References: <20200801130856.86625-1-chenzhou10@huawei.com> <20200801130856.86625-4-chenzhou10@huawei.com> <20200902170910.GB16673@gaia> CC: , , , , , , , , , , , , , , , , , , , , , From: chenzhou Message-ID: Date: Thu, 3 Sep 2020 19:26:27 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20200902170910.GB16673@gaia> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.176.220] X-CFilter-Loop: Reflected Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hi Catalin, On 2020/9/3 1:09, Catalin Marinas wrote: > On Sat, Aug 01, 2020 at 09:08:54PM +0800, Chen Zhou wrote: >> There are following issues in arm64 kdump: >> 1. We use crashkernel=X to reserve crashkernel below 4G, which >> will fail when there is no enough low memory. >> 2. If reserving crashkernel above 4G, in this case, crash dump >> kernel will boot failure because there is no low memory available >> for allocation. >> 3. Since commit 1a8e1cef7603 ("arm64: use both ZONE_DMA and ZONE_DMA32"), >> if the memory reserved for crash dump kernel falled in ZONE_DMA32, >> the devices in crash dump kernel need to use ZONE_DMA will alloc >> fail. >> >> To solve these issues, change the behavior of crashkernel=X. >> crashkernel=X tries low allocation in ZONE_DMA, and fall back to >> high allocation if it fails. >> >> If requized size X is too large and leads to very little free memory >> in ZONE_DMA after low allocation, the system may not work normally. >> So add a threshold and go for high allocation directly if the required >> size is too large. The value of threshold is set as the half of >> the low memory. >> >> If crash_base is outside ZONE_DMA, try to allocate at least 256M in >> ZONE_DMA automatically. "crashkernel=Y,low" can be used to allocate >> specified size low memory. > Except for the threshold to keep zone ZONE_DMA memory, > reserve_crashkernel() looks very close to the x86 version. Shall we try > to make this generic as well? In the first instance, you could avoid the > threshold check if it takes an explicit ",high" option. Ok, i will try to do this. I look into the function reserve_crashkernel() of x86 and found the start address is CRASH_ALIGN in function memblock_find_in_range(), which is different with arm64. I don't figure out why is CRASH_ALIGN in x86, is there any specific reason? Thanks, Chen Zhou