Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946070AbWKJJDS (ORCPT ); Fri, 10 Nov 2006 04:03:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1946087AbWKJJDS (ORCPT ); Fri, 10 Nov 2006 04:03:18 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:34535 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S1946070AbWKJJDQ (ORCPT ); Fri, 10 Nov 2006 04:03:16 -0500 Date: Fri, 10 Nov 2006 10:03:03 +0100 From: Pavel Machek To: Mikulas Patocka Cc: Albert Cahalan , linux-kernel@vger.kernel.org Subject: Re: 2048 CPUs [was: Re: New filesystem for Linux] Message-ID: <20061110090303.GB3196@elf.ucw.cz> References: <787b0d920611041154l69db46abv4c8c467809ada57c@mail.gmail.com> <20061107212614.GA6730@ucw.cz> <20061107231456.GB7796@elf.ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1391 Lines: 36 Hi! > >>If some rogue threads (and it may not even be intetional) call the same > >>syscall stressing the one spinlock all the time, other syscalls needing > >>the same spinlock may stall. > > > >Fortunately, they'll unstall with probability of 1... so no, I do not > >think this is real problem. > > You can't tell that CPUs behave exactly probabilistically --- it may > happen that one gets out of the wait loop always too late. Well, I don't need them to be _exactly_ probabilistical. Anyway, if you have 2048 CPUs... you can perhaps get some non-broken ones. > >If someone takes semaphore in syscall (we do), same problem may > >happen, right...? Without need for 2048 cpus. Maybe semaphores/mutexes > >are fair (or mostly fair) these days, but rwlocks may not be or > >something. > > Scheduler increases priority of sleeping process, so starving process > should be waken up first. But if there are so many processes, that >process I do not think this is how Linux scheduler works. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - 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/