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Tue, 14 Oct 2025 01:34:10 -0700 (PDT) Date: Tue, 14 Oct 2025 01:34:07 -0700 From: Breno Leitao To: Pratyush Yadav Cc: Changyuan Lyu , rppt@kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, anthony.yznaga@oracle.com, arnd@arndb.de, ashish.kalra@amd.com, benh@kernel.crashing.org, bp@alien8.de, catalin.marinas@arm.com, corbet@lwn.net, dave.hansen@linux.intel.com, devicetree@vger.kernel.org, dwmw2@infradead.org, ebiederm@xmission.com, graf@amazon.com, hpa@zytor.com, jgowans@amazon.com, kexec@lists.infradead.org, krzk@kernel.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, luto@kernel.org, mark.rutland@arm.com, mingo@redhat.com, pasha.tatashin@soleen.com, pbonzini@redhat.com, peterz@infradead.org, robh@kernel.org, rostedt@goodmis.org, saravanak@google.com, skinsburskii@linux.microsoft.com, tglx@linutronix.de, thomas.lendacky@amd.com, will@kernel.org, x86@kernel.org Subject: Re: [PATCH v8 01/17] memblock: add MEMBLOCK_RSRV_KERN flag Message-ID: <2ege2jfbevtunhxsnutbzde7cqwgu5qbj4bbuw2umw7ke7ogcn@5wtskk4exzsi> References: <20250509074635.3187114-1-changyuanl@google.com> <20250509074635.3187114-2-changyuanl@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Stat-Signature: cwg8wnzf9goyczw3bu89e5fzr58q8p7c X-Rspam-User: X-Rspamd-Queue-Id: 9B43816000C X-HE-Tag: 1760430852-72101 X-HE-Meta: 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 IaJVVnd+ Z1pmNBd66sB1Agxnaiex2MyMQXUygQ5I4xRoqEJa1c1vqGmHdyuELH046hok8zlb98b3HDHkBfJ7QEJWq1G2CDb8r8qdxtO2ISFBun7cUb/zOJF4KtRGv/Wi2VwwGzHSjgDOtA3yk7pzj9uWcSOEkPfycPKniTjXZ+gbO4wbbd3V3+z306fwaKDuixviPUK09tE1bD/cHCF0wkWvy8o/I8xnl5zrWJMdXZKhIij6TIbhZ+0k6zKnHG3hNZXlyuLO2eLBf23KVtrphCyeC38ufvUBLPZLMMwpZVCFVPz0RmWyo0j9AswpfsxofAAXuCStlq8A/fzVvU4G4lfanThUm2cEN/aKcN9N0HlrCRoTVGBqOFad8jtw270eugQ9s5ya2//MeLsD+/QHLKQx7KGF6uB7Jizhiz7hvJ+Vr49MEa89O24WYgKvbwFRQKOTyGWf/cd+fg10L22zS7Qo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello Pratyush, On Mon, Oct 13, 2025 at 06:40:09PM +0200, Pratyush Yadav wrote: > On Mon, Oct 13 2025, Pratyush Yadav wrote: > > > > I suppose this would be useful. I think enabling memblock debug prints > > would also be helpful (using the "memblock=debug" commandline parameter) > > if it doesn't impact your production environment too much. > > Actually, I think "memblock=debug" is going to be the more useful thing > since it would also show what function allocated the overlapping range > and the flags it was allocated with. > > On my qemu VM with KVM, this results in around 70 prints from memblock. > So it adds a bit of extra prints but nothing that should be too > disrupting I think. Plus, only at boot so the worst thing you get is > slightly slower boot times. Unfortunately this issue is happening on production systems, and I don't have an easy way to reproduce it _yet_. At the same time, "memblock=debug" has two problems: 1) It slows the boot time as you suggested. Boot time at large environments is SUPER critical and time sensitive. It is a bit weird, but it is common for machines in production to kexec _thousands_ of times, and kexecing is considered downtime. This would be useful if I find some hosts getting this issue, and then I can easily enable the extra information to collect what I need, but, this didn't pan out because the hosts I got `memblock=debug` didn't collaborate. 2) "memblock=debug" is verbose for all cases, which also not necessary the desired behaviour. I am more interested in only being verbose when there is a known problem. That said, my suggestion is to only dump extra information when something goes wrong, not affecting the boot time neither boot verbosity.