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[213.44.141.166]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3825fbedf40sm2418281f8f.98.2024.11.22.05.56.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 Nov 2024 05:56:36 -0800 (PST) From: Valentin Schneider To: paulmck@kernel.org Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, x86@kernel.org, rcu@vger.kernel.org, linux-kselftest@vger.kernel.org, Steven Rostedt , Masami Hiramatsu , Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Paolo Bonzini , Wanpeng Li , Vitaly Kuznetsov , Andy Lutomirski , Peter Zijlstra , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Josh Poimboeuf , Jason Baron , Kees Cook , Sami Tolvanen , Ard Biesheuvel , Nicholas Piggin , Juerg Haefliger , Nicolas Saenz Julienne , "Kirill A. Shutemov" , Nadav Amit , Dan Carpenter , Chuang Wang , Yang Jihong , Petr Mladek , "Jason A. Donenfeld" , Song Liu , Julian Pidancet , Tom Lendacky , Dionna Glaze , Thomas =?utf-8?Q?Wei=C3=9Fschuh?= , Juri Lelli , Marcelo Tosatti , Yair Podemsky , Daniel Wagner , Petr Tesarik Subject: Re: [RFC PATCH v3 04/15] rcu: Add a small-width RCU watching counter debug option In-Reply-To: References: <20241119153502.41361-1-vschneid@redhat.com> <20241119153502.41361-5-vschneid@redhat.com> Date: Fri, 22 Nov 2024 14:56:34 +0100 Message-ID: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: u1T2zK5V7MrS2JHD7qP_2HeucF0r0f8868P7COQsmEo_1732283798 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Stat-Signature: cck3cp1oififxmaoczkhnqw3jj61e5ii X-Rspamd-Queue-Id: 020EBC000A X-Rspamd-Server: rspam08 X-Rspam-User: X-HE-Tag: 1732283776-972371 X-HE-Meta: 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 Q7hHfpMf 29qUjgndSkBckRdIW5kEDTTq1HRzGQaIThlDjs/4PeTio0xwgswve0T7y0gPW9Od2CeHbdfr7uFKQN0xskMm1pippiHJcdJm7w29MoKCyaJGSd0z6G8f+iARnXAPeqvABv6n+o9/ty67IJ6y92ZACprWZYZqUGX8A7dQXjKFCzWzemtimLZKG19bTe2V+qfD2hkCECIlbOJJM1uBolRhBgEo38IkBsiG4FiuSZEBOAFcKo2+PiwQfhLMXtQMj59sd02KPcRbpkBcEPj7ltte0ezmL0V2rbH/ogMoqA4OlKDIVlqH1bt6m0FC/ssf5pLBTz6M87e7pSXGYCgp1NY+aMcU9biroteedOVHDXJsti9C8DHl9/YY2nObJXNvpFvPjVCV8 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: On 22/11/24 04:53, Paul E. McKenney wrote: > On Tue, Nov 19, 2024 at 04:34:51PM +0100, Valentin Schneider wrote: >> +config RCU_DYNTICKS_TORTURE >> + bool "Minimize RCU dynticks counter size" >> + depends on RCU_EXPERT >> + default n >> + help >> + This option controls the width of the dynticks counter. >> + >> + Lower values will make overflows more frequent, which will increase >> + the likelihood of extending grace-periods. This option sets the width >> + to its minimum usable value. > > The second sentence ("Lower values ...") sounds at first reading like > this Kconfig option directly controls the width. The third sentence sets > things straight, but the reader might well be irretrievably confused by > that point. How about something like this instead? > > help > This option sets the width of the dynticks counter to its > minimum usable value. This minimum width greatly increases > the probability of flushing out bugs involving counter wrap, > but it also increases the probability of extending grace period > durations. This Kconfig option should therefore be avoided in > production due to the consequent increased probability of OOMs. > > This has no value for production and is only for testing. > Much better, I'll take that, thank you! >> endmenu # "RCU Debugging" >> -- >> 2.43.0 >>