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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-46c9ed7491esm4146372f8f.37.2026.06.24.08.48.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jun 2026 08:48:28 -0700 (PDT) Date: Wed, 24 Jun 2026 16:48:26 +0100 From: David Laight To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Linus Torvalds , Sebastian Andrzej Siewior , John Ogness , Thomas Gleixner , Peter Zijlstra , Julia Lawall , Yury Norov Subject: Re: [PATCH v3 2/2] tracing: Remove trace_printk.h from kernel.h Message-ID: <20260624164826.56a7f7b4@pumpkin> In-Reply-To: <20260624103225.77116713@fedora> References: <20260624081806.120105649@kernel.org> <20260624081948.301578807@kernel.org> <20260624111152.75476a46@pumpkin> <20260624103225.77116713@fedora> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) 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-Transfer-Encoding: 7bit On Wed, 24 Jun 2026 10:32:25 -0400 Steven Rostedt wrote: > On Wed, 24 Jun 2026 11:11:52 +0100 > David Laight wrote: > > > That is all about changes to the file causing everything to be rebuilt, > > not the contents of the file slowing down builds. > > I guess I should say it better. It causes more build time if that file > changes. That's what I meant. I update the wording to say: > > There have been complaints about trace_printk.h causing more build time > for being in kernel.h it if changes. There is also an effort to clean up > kernel.h to have it not include unneeded header files. Move trace_printk.h > out of kernel.h and place it in the headers and C files that use it. > > > > The part you are moving out of normal builds is just a few #defines. > > They won't have a significant effect on build times either. > > > > So there is no point splitting out trace_controls.h. > > That is a completely different reason. trace_printk.h is about > trace_printk() usage. The stuff split out into trace_controls.h have > nothing to do with trace_printk()s. True, but every header file costs extra time to open. That could easily be more that the cost of parsing it (ok hand waving!). With a long list of -I parameters just finding a file costs because of all the failed opens. I've just knocked it out of kernel.h, had to fix: rcu.h linux/ftrace.h to make my 'normal' kernel build. Lots of stuff includes the latter. David > > -- Steve >