Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262491AbVAEPsF (ORCPT ); Wed, 5 Jan 2005 10:48:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262465AbVAEPio (ORCPT ); Wed, 5 Jan 2005 10:38:44 -0500 Received: from mustang.oldcity.dca.net ([216.158.38.3]:4229 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S262470AbVAEPT6 (ORCPT ); Wed, 5 Jan 2005 10:19:58 -0500 Subject: Re: [PATCH] [request for inclusion] Realtime LSM From: Lee Revell To: Ingo Molnar Cc: Chris Wright , Alan Cox , "Jack O'Quin" , Christoph Hellwig , Linux Kernel Mailing List , Andrew Morton , Arjan van de Ven In-Reply-To: <20050105115213.GA17816@elte.hu> References: <1104374603.9732.32.camel@krustophenia.net> <20050103140359.GA19976@infradead.org> <1104862614.8255.1.camel@krustophenia.net> <20050104182010.GA15254@infradead.org> <87u0pxhvn0.fsf@sulphur.joq.us> <1104865198.8346.8.camel@krustophenia.net> <1104878646.17166.63.camel@localhost.localdomain> <20050104175043.H469@build.pdx.osdl.net> <1104890131.18410.32.camel@krustophenia.net> <20050105115213.GA17816@elte.hu> Content-Type: text/plain Date: Wed, 05 Jan 2005 10:19:53 -0500 Message-Id: <1104938394.8589.5.camel@krustophenia.net> Mime-Version: 1.0 X-Mailer: Evolution 2.0.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2029 Lines: 41 On Wed, 2005-01-05 at 12:52 +0100, Ingo Molnar wrote: > the RT-LSM thing is a bit dangerous because it doesnt really protect > against a runaway, buggy app. So i think the right way to approach this > problem is to not apply RT-LSM for the time being, but to provide an > 'advanced latency needs' scheduling class that is _still_ safe even if > the task is runaway, but behaves with near-RT priorities if the task is > 'nice' (i.e. doesnt use up large amount of CPU time.) > > incidentally, there is such a scheduling class already: negative nice > levels. Please skip any preconceptions you might have about nice levels, > nice levels have been improved in 2.6.10, the timeslices are now given > out exponentially, giving nice -20 tasks far more weight and priority > than they used to have. (They are obviously still preemptable if they > keep looping burning CPU - but that we can consider a feature.) (Also, > in 2.6 the negative nice levels have a much more agressive interactivity > setting, allowing them to preempt everything lower-prio.) > > so, could you try vanilla 2.6.10 (without LSM and without jackd running > with RT priorities), with jackd set to nice -20? Make sure the > jack-client process gets this priority too. Best to achieve this is to > renice a shell to -20 and start up everything from there - the nice > settings will be inherited. How does such an audio test compare to a > test done with jackd running at SCHED_FIFO with RT priority 1? > > if this works out well then we could achieve something comparable to > RT-LSM, via nice levels alone. > Adding Paul Davis to the cc:, as he has expressed very strong opinions on this in the past. Of course this does not address the problem as you still need to be root to run at a negative nice value. Lee - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/