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,URIBL_BLOCKED,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 30B3BC43461 for ; Thu, 3 Sep 2020 14:57:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0858D2065F for ; Thu, 3 Sep 2020 14:57:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729464AbgICO4e (ORCPT ); Thu, 3 Sep 2020 10:56:34 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:10764 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729175AbgICOKy (ORCPT ); Thu, 3 Sep 2020 10:10:54 -0400 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id C91757B51C7D80ACF500; Thu, 3 Sep 2020 21:18:59 +0800 (CST) Received: from [127.0.0.1] (10.174.176.220) by DGGEMS405-HUB.china.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.487.0; Thu, 3 Sep 2020 21:18:53 +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: <779fd86d-4d1a-c2ac-ffc8-79f05526a00c@huawei.com> Date: Thu, 3 Sep 2020 21:18:51 +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: Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.176.220] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/9/3 19:26, chenzhou wrote: > 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? Besides, in function reserve_crashkernel_low() of x86, the start address is 0. > > Thanks, > Chen Zhou > > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > . >