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AJvYcCUtSCxPY0VQzicgmsYNlFhIzwrfYgxFcULPG4SVAymCXZcRFR2mdJ+ob2xSWRs5SGAC91iqpcP2QQ==@kvack.org X-Gm-Message-State: AOJu0YzxYZptMhw9kC4oi6nGJmqZeUMjN3JB4F+wHN05N1zh0ql5sE1o c3+TUoRIzFHp6uOwDcXc1/bSDugaCbhJLeiwl4y9kK2+QGMLJTRrflqCIjuJUXkDKkCwdww8T7X Izt5mUEwF+Q== X-Google-Smtp-Source: AGHT+IG1H8EWFmTdy9mXUfcCJxQBprr6abVa1X9treBvRrD020Cub+yFF9voa0K8UUVl5WCrL4gH+SDc7+SKLQ== X-Received: from wmbel14.prod.google.com ([2002:a05:600c:3e0e:b0:440:5f8a:667c]) (user=jackmanb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:4ec6:b0:43d:a90:9f1 with SMTP id 5b1f17b1804b1-441b2635482mr61130455e9.6.1746112976936; Thu, 01 May 2025 08:22:56 -0700 (PDT) Date: Thu, 01 May 2025 15:22:55 +0000 In-Reply-To: <20250501150229.GU4439@noisy.programming.kicks-ass.net> Mime-Version: 1.0 References: <20250429-noautoinline-v3-0-4c49f28ea5b5@uniontech.com> <20250429123504.GA13093@lst.de> <20250501150229.GU4439@noisy.programming.kicks-ass.net> X-Mailer: aerc 0.20.0 Message-ID: Subject: Re: [PATCH RFC v3 0/8] kernel-hacking: introduce CONFIG_NO_AUTO_INLINE From: Brendan Jackman To: Peter Zijlstra Cc: Christoph Hellwig , , Keith Busch , Jens Axboe , Sagi Grimberg , Andrew Morton , Yishai Hadas , Jason Gunthorpe , Shameer Kolothum , Kevin Tian , Alex Williamson , Peter Huewe , Jarkko Sakkinen , Masahiro Yamada , Nathan Chancellor , Nicolas Schier , Nick Desaulniers , Bill Wendling , Justin Stitt , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Johannes Weiner , Zi Yan , Mathieu Desnoyers , "Paul E. McKenney" , Boqun Feng , Dmitry Vyukov , Andrey Konovalov , Juergen Gross , Boris Ostrovsky , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , , "H. Peter Anvin" , , , , , , , , , Winston Wen , , , Changbin Du , Linus Torvalds Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: B0FAA40005 X-Stat-Signature: f4o5dz8mhbt9cg79see96pf53ao1zyfz X-HE-Tag: 1746112978-4318 X-HE-Meta: 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 HCOldDF2 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 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 Thu May 1, 2025 at 3:02 PM UTC, Peter Zijlstra wrote: > On Thu, May 01, 2025 at 02:19:47PM +0000, Brendan Jackman wrote: >> On Tue Apr 29, 2025 at 12:35 PM UTC, Christoph Hellwig wrote: >> > On Tue, Apr 29, 2025 at 12:06:04PM +0800, Chen Linxuan via B4 Relay wrote: >> >> This series introduces a new kernel configuration option NO_AUTO_INLINE, >> >> which can be used to disable the automatic inlining of functions. >> >> >> >> This will allow the function tracer to trace more functions >> >> because it only traces functions that the compiler has not inlined. >> > >> > This still feels like a bad idea because it is extremely fragile. >> >> Can you elaborate on that - does it introduce new fragility? > > given it needs to sprinkle __always_inline around where it wasn't needed > before, yeah. Right, I guess I just wouldn't have associated that with the word "fragility", but that's a reasonable complaint! > Also, why would you want this? function tracer is already too much > output. Why would you want even more? Yes, tracing every function is already too noisy, this would make it even more too-noisy, not sure "too noisy" -> "way too noisy" is a particularly meaningful degradation. Whereas enlarging the pool of functions that you can _optionally target_ for tracing, or nice reliable breakpoints in GDB, and disasm that's easier to mentally map back to C, seems like a helpful improvement for test builds. Personally I sometimes spam a bunch of `noinline` into code I'm debugging so this seems like a way to just slap that same thing on the whole tree without dirtying the code, right? Not that I have a strong opinion on the cost/benefit here, but the benefit seems nonzero to me.