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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id d2sm1225711wrq.94.2019.03.05.23.08.37 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 05 Mar 2019 23:08:38 -0800 (PST) Date: Wed, 6 Mar 2019 08:08:36 +0100 From: Ingo Molnar To: Linus Torvalds Cc: Linux List Kernel Mailing , "Paul E. McKenney" , Thomas Gleixner , Peter Zijlstra , Andrew Morton Subject: Re: [GIT PULL] RCU updates for v5.1 Message-ID: <20190306070836.GA111385@gmail.com> References: <20190305120301.GA93284@gmail.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 * Linus Torvalds wrote: > On Tue, Mar 5, 2019 at 4:03 AM Ingo Molnar wrote: > > > > Please pull the latest core-rcu-for-linus git tree from: > > > > git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core-rcu-for-linus > > Hmm. I think this made my build time explode. > > I'm bisecting, but it looks like my allmodconfig builds went from ~31 > min to ~39 min with this pull. > > NOTE! I'm not saying that the kernel slowed down. Just the *build* > (with the same kernel) slowed down. > > It's odd, and maybe I did something wrong, so I'll have to > double-check the numbers, but I thought I'd mention it in case > somebody goes "Ahh, I did X to the include files, so now every > compiler invocation probably sees all of xyz and that will slow things > down enormously". Could it be the locking tree? In particular the atomics auto-generation slowed down the build before, but this build regression was thought to be fixed with: 0cf264b3133d: locking/atomics: Check atomic headers with sha1sum but maybe that's not the whole story? Or it's an unreported slowdown related to the RCU tree, as you say. Thanks, Ingo