From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-174.mta0.migadu.com (out-174.mta0.migadu.com [91.218.175.174]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 97F0531326B for ; Fri, 17 Apr 2026 09:23:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.174 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776417837; cv=none; b=mkIcp8tmLiA/yFzHdPXWMuojzkQNLPCGQuJoplQEvRqbql8fRuM4FMk48u9hwcvxhAeIS+nWib13hVARDdYkoxPQDjJFnV6Gikoat1VBOE5Vabyk03gr21HAysjEPAfLPZ6IOCxNNif4dLoxcvbLsh4sYzwRCBu+SbJKyaX386g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776417837; c=relaxed/simple; bh=bxhLWlsH38nctCN2Sqtp0FNUJjg3XOl8ORoFvMkTgNY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hQJ+H0JL60F89Wz4T9r5smPBVvlNdX/IQ17qFgP9gAFKa/+0vwKUebkLsaEM1XEri2ORJH56OmNGT2eAPgT1PiZTXh25/UOBHUjseilytHAnLZRYA8bM8agRTgPISzIMaH8JjtIf1yOiT8PMxqGH9ZoG5LTs5e2Mp27R8/gOhvY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=GeHGYql+; arc=none smtp.client-ip=91.218.175.174 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="GeHGYql+" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1776417833; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bxhLWlsH38nctCN2Sqtp0FNUJjg3XOl8ORoFvMkTgNY=; b=GeHGYql+K62K8092FrXUYkINVPGvfXquj4jyvdTo+JSuGTjL5B8ClIhv1zP7YKhBMDtf0/ NGGgAAwA2FD9QX03Un9qjIK61VERnBWP7G8rwQ7IkhurYQCIzE3WLR2PRxiZ1w2gZLXQta MJuHFpGc5a2dC95vxgwH+m5V1dETojQ= Date: Fri, 17 Apr 2026 17:23:12 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH] crash: Support high memory reservation for range syntax To: Baoquan He Cc: Baoquan He , Sourabh Jain , Andrew Morton , Jonathan Corbet , Vivek Goyal , Dave Young , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Youling Tang References: <20260404074103.506793-1-youling.tang@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Youling Tang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 4/15/26 19:29, Baoquan He wrote: > On 04/09/26 at 09:55am, Youling Tang wrote: >> Hi, Baoquan >> >> On 4/8/26 21:32, Baoquan He wrote: >>> On 04/08/26 at 10:01am, Sourabh Jain wrote: >>>> Hello Youling, >>>> >>>> On 04/04/26 13:11, Youling Tang wrote: >>>>> From: Youling Tang >>>>> >>>>> The crashkernel range syntax (range1:size1[,range2:size2,...]) allows >>>>> automatic size selection based on system RAM, but it always reserves >>>>> from low memory. When a large crashkernel is selected, this can >>>>> consume most of the low memory, causing subsequent hardware >>>>> hotplug or drivers requiring low memory to fail due to allocation >>>>> failures. >>>> Support for high crashkernel reservation has been added to >>>> address the above problem. >>>> >>>> However, high crashkernel reservation is not supported with >>>> range-based crashkernel kernel command-line arguments. >>>> For example: crashkernel=0M-1G:100M,1G-4G:160M,4G-8G:192M >>>> >>>> Many users, including some distributions, use range-based >>>> crashkernel configuration. So, adding support for high crashkernel >>>> reservation with range-based configuration would be useful. >>> Sorry for late response. And I have to say sorry because I have some >>> negative tendency on this change. >>> >>> We use crashkernel=xM|G and crashkernel=range1:size1[,range2:size2,...] >>> as default setting, so that people only need to set suggested amount >>> of memory. While crashkernel=,high|low is for advanced user to customize >>> their crashkernel value. In that case, user knows what's high memory and >>> low memory, and how much is needed separately to achieve their goal, e.g >>> saving low memory, taking away more high memory. >>> >>> To be honest, above grammers sounds simple, right? I believe both of you >>> know very well how complicated the current crashkernel code is. I would >>> suggest not letting them becomre more and more complicated by extending >>> the grammer further and further. Unless you meet unavoidable issue with >>> the existing grammer. >>> >>> Here comes my question, do you meet unavoidable issue with the existing >>> grammer when you use crashkernel=range1:size1[,range2:size2,...] and >>> think it's not satisfactory, and at the same time crashkernel=,high|low >>> can't meet your demand either? >> Yes, regular users generally don't know about high memory and low memory, >> and probably don't know how much crashkernel memory should be reserved >> either. They mostly just use the default crashkernel parameters configured >> by the distribution. >> >> For advanced users, the current grammar is sufficient, because >> 'crashkernel=:[,:,...][@offset],>boundary' >> can definitely be replaced with 'crashkernel=size,high'. >> >> The main purpose of this patch is to provide distributions with a more >> reasonable default parameter configuration (satisfying most requirements), >> without having to set different distribution default parameters for >> different >> scenarios (physical machines, virtual machines) and different machine >> models. > OK, do you have a concrete case? e.g in your distros, what will you set > with this patchset applied? Let's see if it can cover all cases with one > simple and satisfying parameter. For our production deployment across various hardware configurations (physical servers, VMs with different memory sizes), I'm planning to use the following crashkernel configuration: crashkernel=1G-4G:256M,4G-12G:384M,12G-48G:512M,48G-128G:768M,128G-:1024M,>384M Thanks, Youling.