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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id q125sm1177385wme.33.2018.11.28.00.30.59 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 28 Nov 2018 00:31:00 -0800 (PST) Date: Wed, 28 Nov 2018 09:30:57 +0100 From: Ingo Molnar To: Mark Rutland Cc: tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org, peterz@infradead.org, boqun.feng@gmail.com, will.deacon@arm.com, linux-tip-commits@vger.kernel.org, akpm@linux-foundation.org, torvalds@linux-foundation.org Subject: Re: [tip:locking/core] locking/atomics: Check generated headers are up-to-date Message-ID: <20181128083057.GA7879@gmail.com> References: <20180904104830.2975-6-mark.rutland@arm.com> <20181121080258.GA56691@gmail.com> <20181121114028.iiuleuwuayednvut@salmiak> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181121114028.iiuleuwuayednvut@salmiak> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Mark Rutland wrote: > > Could we please get this fixed so that proper dependencies are checked > > and it's only regenerated when needed? This slowdown makes additive-build > > kernel development quite painful, as ~5 seconds is in the 'too long' > > category already, while 1.2 seconds is basically instantaneous. > > Just to check, are we happy to eat the full cost for the first build of a > pristine tree? No, not happy to add 3-4 seconds to a full build that usually takes less than 60 seconds. This stuff isn't parallelized nor particularly well optimized it appears. This *must* get faster. > One reason we do the check rather than (re-)generating the headers is > that Linus requested [1] the generated header be committed so that they > show up in git grep, but it looks like he was happy to be flexible on > that. I think the generated headers should be part of the commit space, the grepping is important. > If we're happy to not commit in the generated headers, and if we're happy to > pay the cost for a pristine tree, that's fairly straightforward to do. > Otherwise, this has to be an optional check. Or faster code, or a different concept! Thanks, Ingo