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[209.85.208.171]) by smtp.gmail.com with ESMTPSA id 10sm101182ljw.134.2020.06.01.12.56.23 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Jun 2020 12:56:23 -0700 (PDT) Received: by mail-lj1-f171.google.com with SMTP id z6so9652884ljm.13 for ; Mon, 01 Jun 2020 12:56:23 -0700 (PDT) X-Received: by 2002:a2e:b5d7:: with SMTP id g23mr4660105ljn.70.1591041383289; Mon, 01 Jun 2020 12:56:23 -0700 (PDT) MIME-Version: 1.0 References: <20200601130806.GA746506@gmail.com> In-Reply-To: <20200601130806.GA746506@gmail.com> From: Linus Torvalds Date: Mon, 1 Jun 2020 12:56:07 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [GIT PULL] kprobes updates for v5.8 To: Ingo Molnar Cc: Linux Kernel Mailing List , Peter Zijlstra , Thomas Gleixner , Borislav Petkov , Andrew Morton Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 1, 2020 at 6:08 AM Ingo Molnar wrote: > > include/linux/compiler.h | 53 +++++++++++++++++++++++ I have pulled this, but do we really want to add this to a header file that is _so_ core that it gets included for basically every single file built? I don't even see those instrumentation_begin/end() things used anywhere right now. It seems excessive. That 53 lines is maybe not a lot, but it pushed that header file to over 12kB, and while it's mostly comments, it's extra IO and parsing basically for _every_ single file compiled in the kernel. For what appears to be absolutely zero upside right now, and I really don't see why this should be in such a core header file! I don't even see this as having anything at all to do with "compiler.h" in the first place. I really think we should think twice about making core header files bigger like this. No, we're nowhere the disaster that C++ project headers are, but tokenization and parsing is actually a pretty big part of the build costs (which may surprise some people who think it's all the fancy optimizations that cost a lot of CPU time). Linus