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[109.81.89.112]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3a4f0097205sm1148358f8f.79.2025.05.29.00.46.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 May 2025 00:46:27 -0700 (PDT) Date: Thu, 29 May 2025 09:46:26 +0200 From: Michal Hocko To: David Hildenbrand Cc: Baoquan He , Donald Dutile , Jiri Bohac , Vivek Goyal , Dave Young , kexec@lists.infradead.org, Philipp Rudo , Pingfan Liu , Tao Liu , linux-kernel@vger.kernel.org, David Hildenbrand Subject: Re: [PATCH v2 0/5] kdump: crashkernel reservation from CMA Message-ID: References: <04904e86-5b5f-4aa1-a120-428dac119189@redhat.com> <427fec88-2a74-471e-aeb6-a108ca8c4336@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed 28-05-25 23:01:04, David Hildenbrand wrote: [...] > I think we just have to be careful to document it properly -- especially the > shortcomings and that this feature might become a problem in the future. > Movable user-space page tables getting placed on CMA memory would probably > not be a problem if we don't care about ... user-space data either way. I think makedumpfile could refuse to capture a dump if userspace memory is requested to enforce this. > The whole "Direct I/O takes max 1s" part is a bit shaky. Maybe it could be > configurable how long to wait? 10s is certainly "safer". Quite honestly we will never know and rather than making this configurable I would go with reasonably large. Couple of seconds certainly do not matter for the kdump situations but I would go as far as minutes. -- Michal Hocko SUSE Labs