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From: Baoquan He To: Youling Tang 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 Subject: Re: [PATCH] crash: Support high memory reservation for range syntax Message-ID: References: <20260404074103.506793-1-youling.tang@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260415_042928_227557_F71CAA7D X-CRM114-Status: GOOD ( 26.51 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org 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.