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[193.205.81.5]) by smtp.gmail.com with ESMTPSA id 126-v6sm19437345wme.48.2018.10.10.06.48.56 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Oct 2018 06:48:57 -0700 (PDT) Subject: Re: [RFD/RFC PATCH 0/8] Towards implementing proxy execution To: Peter Zijlstra , Henrik Austad Cc: Juri Lelli , mingo@redhat.com, rostedt@goodmis.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it, claudio@evidence.eu.com, tommaso.cucinotta@santannapisa.it, alessio.balsini@gmail.com, will.deacon@arm.com, andrea.parri@amarulasolutions.com, dietmar.eggemann@arm.com, patrick.bellasi@arm.com, linux-rt-users@vger.kernel.org References: <20181009092434.26221-1-juri.lelli@redhat.com> <20181010115639.GA25534@sisyphus.home.austad.us> <20181010122454.GR5663@hirez.programming.kicks-ass.net> From: Daniel Bristot de Oliveira Message-ID: Date: Wed, 10 Oct 2018 15:48:56 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <20181010122454.GR5663@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/10/18 2:24 PM, Peter Zijlstra wrote: >> I believe there were some papers circulated last year that looked at >> something similar to this when you had overlapping or completely disjoint >> CPUsets I think it would be nice to drag into the discussion. Has this been >> considered? (if so, sorry for adding line-noise!) > Hurm, was that one of Bjorn's papers? Didn't that deal with AC of > disjoint/overlapping sets? > This paper: https://people.mpi-sws.org/~bbb/papers/pdf/rtsj14.pdf But, unless I am wrong, there were findings after this paper that shows some imprecision on it. Anyway, it does not analyse the locking properties, only scheduler of independent tasks - it is a start, but far from what we do here. (btw this paper is really complex...) The locking problem for such case: APA with the nesting of different locks in the locking implementation (we use raw spin lock on this, and this method could also be used in the rw lock/sem in the future, nesting rw_lock(mutex_proxy(raw_spinlock())) is an open problem from the academic point of view. I explained these things (nested lock and the need of APA for locking) as "Open Problems" at the RTSOPs (part of the ECRTS) earlier this year: http://rtsops2018.loria.fr/wp-content/uploads/2018/07/RTSOPS18_proceedings_final.pdf Bjorn were there, but not only him... Baruah, Davis, Alan Burns were there. There are some works being done for more complex locking in academy, like: https://www.cs.unc.edu/~jarretc/papers/ecrts18b_long.pdf But still, the task model used on these implementations are not the Linux one. -- Daniel