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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id x136sm443029wme.0.2018.11.21.00.03.00 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 21 Nov 2018 00:03:00 -0800 (PST) Date: Wed, 21 Nov 2018 09:02:58 +0100 From: Ingo Molnar To: mark.rutland@arm.com, tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org, peterz@infradead.org, boqun.feng@gmail.com, will.deacon@arm.com Cc: linux-tip-commits@vger.kernel.org Subject: Re: [tip:locking/core] locking/atomics: Check generated headers are up-to-date Message-ID: <20181121080258.GA56691@gmail.com> References: <20180904104830.2975-6-mark.rutland@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 * tip-bot for Mark Rutland wrote: > Commit-ID: 8d32588077bdc390420cfa6946f407033a20d7a8 > Gitweb: https://git.kernel.org/tip/8d32588077bdc390420cfa6946f407033a20d7a8 > Author: Mark Rutland > AuthorDate: Tue, 4 Sep 2018 11:48:29 +0100 > Committer: Ingo Molnar > CommitDate: Thu, 1 Nov 2018 11:01:10 +0100 > > locking/atomics: Check generated headers are up-to-date > > Now that all the generated atomic headers are in place, it would be good > to ensure that: > > a) the headers are up-to-date when scripting changes. > > b) developers don't directly modify the generated headers. > > To ensure both of these properties, let's add a Kbuild step to check > that the generated headers are up-to-date. > > Signed-off-by: Mark Rutland > Signed-off-by: Peter Zijlstra (Intel) > Cc: linux-arm-kernel@lists.infradead.org > Cc: catalin.marinas@arm.com > Cc: Will Deacon > Cc: linuxdrivers@attotech.com > Cc: dvyukov@google.com > Cc: Boqun Feng > Cc: arnd@arndb.de > Cc: aryabinin@virtuozzo.com > Cc: glider@google.com > Link: http://lkml.kernel.org/r/20180904104830.2975-6-mark.rutland@arm.com > Signed-off-by: Ingo Molnar > --- > Kbuild | 18 ++++++++++++++++-- > scripts/atomic/check-atomics.sh | 19 +++++++++++++++++++ > 2 files changed, 35 insertions(+), 2 deletions(-) These scripts are *awfully* slow to be run at every kernel build - even a reasonably fast machine: model name : Intel(R) Xeon(R) CPU E5-2680 v2 @ 2.80GHz ... they are adding 3-4 seconds to the build time: [Before]: galatea:~/linux/linux> perf stat --null --repeat 3 make kernel/sched/core.o CALL scripts/checksyscalls.sh DESCEND objtool CALL scripts/checksyscalls.sh DESCEND objtool CALL scripts/checksyscalls.sh DESCEND objtool Performance counter stats for 'make kernel/sched/core.o' (3 runs): 1.201874 +- 0.000371 seconds time elapsed ( +- 0.03% ) [After]: galatea:~/linux/linux> perf stat --null --repeat 3 make kernel/sched/core.o CALL scripts/checksyscalls.sh CALL scripts/atomic/check-atomics.sh DESCEND objtool CALL scripts/checksyscalls.sh CALL scripts/atomic/check-atomics.sh DESCEND objtool CALL scripts/checksyscalls.sh CALL scripts/atomic/check-atomics.sh DESCEND objtool Performance counter stats for 'make kernel/sched/core.o' (3 runs): 4.5987 +- 0.0109 seconds time elapsed ( +- 0.24% ) 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. I cannot even imagine the slowdown on a truly slow box where kernel development *has* to be additive. Thanks, Ingo