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=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 B14BCC433DF for ; Mon, 10 Aug 2020 03:28:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 982522065D for ; Mon, 10 Aug 2020 03:28:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726398AbgHJD2e (ORCPT ); Sun, 9 Aug 2020 23:28:34 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:33034 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726335AbgHJD2e (ORCPT ); Sun, 9 Aug 2020 23:28:34 -0400 Received: from DGGEMS410-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 6375DE9F691D67B7F72E; Mon, 10 Aug 2020 11:28:32 +0800 (CST) Received: from [127.0.0.1] (10.174.176.220) by DGGEMS410-HUB.china.huawei.com (10.3.19.210) with Microsoft SMTP Server id 14.3.487.0; Mon, 10 Aug 2020 11:28:24 +0800 Subject: Re: [PATCH v11 5/5] kdump: update Documentation about crashkernel To: Dave Young References: <20200801130856.86625-1-chenzhou10@huawei.com> <20200801130856.86625-6-chenzhou10@huawei.com> <20200808100239.GB60590@dhcp-128-65.nay.redhat.com> CC: , , , , , , , , , , , , , , , , , , , , , From: chenzhou Message-ID: <96d0da23-d484-7f66-1680-07b4b5984831@huawei.com> Date: Mon, 10 Aug 2020 11:28:22 +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: <20200808100239.GB60590@dhcp-128-65.nay.redhat.com> 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 2020/8/8 18:02, Dave Young wrote: > On 08/01/20 at 09:08pm, Chen Zhou wrote: >> Now the behavior of crashkernel=X has been changed, which 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 well. >> So add a threshold and go for high allocation directly if the required >> size is too large. The threshold is set as the half of 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. For non-RPi4 platforms, change ZONE_DMA >> memtioned above to ZONE_DMA32. >> >> So update the Documentation. >> >> Signed-off-by: Chen Zhou >> --- >> Documentation/admin-guide/kdump/kdump.rst | 21 ++++++++++++++++--- >> .../admin-guide/kernel-parameters.txt | 11 ++++++++-- >> 2 files changed, 27 insertions(+), 5 deletions(-) >> >> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst >> index 2da65fef2a1c..4b58f97351d5 100644 >> --- a/Documentation/admin-guide/kdump/kdump.rst >> +++ b/Documentation/admin-guide/kdump/kdump.rst >> @@ -299,7 +299,15 @@ Boot into System Kernel >> "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory >> starting at physical address 0x01000000 (16MB) for the dump-capture kernel. >> >> - On x86 and x86_64, use "crashkernel=64M@16M". >> + On x86 use "crashkernel=64M@16M". >> + >> + On x86_64, use "crashkernel=X" to select a region under 4G first, and >> + fall back to reserve region above 4G. >> + We can also use "crashkernel=X,high" to select a region above 4G, which >> + also tries to allocate at least 256M below 4G automatically and >> + "crashkernel=Y,low" can be used to allocate specified size low memory. >> + Use "crashkernel=Y@X" if you really have to reserve memory from specified >> + start address X. >> >> On ppc64, use "crashkernel=128M@32M". >> >> @@ -316,8 +324,15 @@ Boot into System Kernel >> kernel will automatically locate the crash kernel image within the >> first 512MB of RAM if X is not given. >> >> - On arm64, use "crashkernel=Y[@X]". Note that the start address of >> - the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000). >> + On arm64, use "crashkernel=X" to try low allocation in ZONE_DMA, and >> + fall back to high allocation if it fails. And go for high allocation >> + directly if the required size is too large. 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. >> + For non-RPi4 platforms, change ZONE_DMA memtioned above to ZONE_DMA32. >> + Use "crashkernel=Y@X" if you really have to reserve memory from >> + specified start address X. Note that the start address of the kernel, >> + X if explicitly specified, must be aligned to 2MiB (0x200000). >> >> Load the Dump-capture Kernel >> ============================ >> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >> index fb95fad81c79..d1b6016850d6 100644 >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -722,6 +722,10 @@ >> [KNL, x86_64] select a region under 4G first, and >> fall back to reserve region above 4G when '@offset' >> hasn't been specified. >> + [KNL, arm64] Try low allocation in ZONE_DMA, fall back >> + to high allocation if it fails when '@offset' hasn't been >> + specified. For non-RPi4 platforms, change ZONE_DMA to >> + ZONE_DMA32. >> See Documentation/admin-guide/kdump/kdump.rst for further details. >> >> crashkernel=range1:size1[,range2:size2,...][@offset] >> @@ -746,13 +750,16 @@ >> requires at least 64M+32K low memory, also enough extra >> low memory is needed to make sure DMA buffers for 32-bit >> devices won't run out. Kernel would try to allocate at >> - at least 256M below 4G automatically. >> + least 256M below 4G automatically. >> This one let user to specify own low range under 4G >> for second kernel instead. >> 0: to disable low allocation. >> It will be ignored when crashkernel=X,high is not used >> or memory reserved is below 4G. >> - >> + [KNL, arm64] range under 4G. >> + This one let user to specify a low range in ZONE_DMA for >> + crash dump kernel. For non-RPi4 platforms, change ZONE_DMA >> + to ZONE_DMA32. >> cryptomgr.notests >> [KNL] Disable crypto self-tests >> >> -- >> 2.20.1 >> > Hi Chen, > > Previously I remember we talked about to use similar logic as X86, but I > remember you mentioned on some arm64 platform there could be no low > memory at all. Is this not a problem now for the fallback? Just be > curious, thanks for the update, for the common part looks good. Hi Dave, Did you mean this discuss: https://lkml.org/lkml/2019/12/27/122? This is about the different implementation instead of no low memory in arm64. On arm64 platform, if there is no low memory, system will boot fail. Thanks, Chen Zhou > > Acked-by: Dave Young > > Thanks > Dave > > > . >