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=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 807BDC433E1 for ; Sat, 8 Aug 2020 10:02:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5C1842075D for ; Sat, 8 Aug 2020 10:02:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Ixlp0mjF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726316AbgHHKC6 (ORCPT ); Sat, 8 Aug 2020 06:02:58 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:38180 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726074AbgHHKC5 (ORCPT ); Sat, 8 Aug 2020 06:02:57 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1596880975; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=9sQZQ3O/mt1wEI6vVEOUOzXH/lCb8p+hxo0Z8dtXlDY=; b=Ixlp0mjFRAGsWmQaMbhNcgIJlLHD40f8dcH0SDkJqeSchohK6n6cPr3iqiqxEXrobFP0fU RtYfo/0AV6qSergsIWhYf3vYvlw6ePyFTTL7h1G1xTtZRC9Df5ZazxsPZmph495iH/45S0 S7oSKht0psAtRnhDyymta3n9lVtL2Uk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-143-4m4wsm1qP9CP0y11zK1KUg-1; Sat, 08 Aug 2020 06:02:53 -0400 X-MC-Unique: 4m4wsm1qP9CP0y11zK1KUg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3171F100960F; Sat, 8 Aug 2020 10:02:51 +0000 (UTC) Received: from dhcp-128-65.nay.redhat.com (ovpn-12-106.pek2.redhat.com [10.72.12.106]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 67E558AC2B; Sat, 8 Aug 2020 10:02:43 +0000 (UTC) Date: Sat, 8 Aug 2020 18:02:39 +0800 From: Dave Young To: Chen Zhou Cc: catalin.marinas@arm.com, will@kernel.org, james.morse@arm.com, tglx@linutronix.de, mingo@redhat.com, bhe@redhat.com, corbet@lwn.net, John.P.donnelly@oracle.com, prabhakar.pkin@gmail.com, bhsharma@redhat.com, horms@verge.net.au, robh+dt@kernel.org, arnd@arndb.de, nsaenzjulienne@suse.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-doc@vger.kernel.org, guohanjun@huawei.com, xiexiuqi@huawei.com, huawei.libin@huawei.com, wangkefeng.wang@huawei.com Subject: Re: [PATCH v11 5/5] kdump: update Documentation about crashkernel Message-ID: <20200808100239.GB60590@dhcp-128-65.nay.redhat.com> References: <20200801130856.86625-1-chenzhou10@huawei.com> <20200801130856.86625-6-chenzhou10@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200801130856.86625-6-chenzhou10@huawei.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Acked-by: Dave Young Thanks Dave