From owner-freebsd-current@FreeBSD.ORG Wed Feb 19 20:32:17 2014 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id C56EE579 for ; Wed, 19 Feb 2014 20:32:17 +0000 (UTC) Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by mx1.freebsd.org (Postfix) with ESMTP id AF333117A for ; Wed, 19 Feb 2014 20:32:17 +0000 (UTC) Received: from Alfreds-MacBook-Pro.local (unknown [50.204.88.5]) by elvis.mu.org (Postfix) with ESMTPSA id F30C21A3C38 for ; Wed, 19 Feb 2014 12:32:16 -0800 (PST) Message-ID: <530514F0.2000609@mu.org> Date: Wed, 19 Feb 2014 12:32:48 -0800 From: Alfred Perlstein User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: freebsd-current@freebsd.org Subject: Re: [rfc] bind per-cpu timeout threads to each CPU References: <530508B7.7060102@FreeBSD.org> <53050D24.3020505@FreeBSD.org> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Feb 2014 20:32:17 -0000 On 2/19/14, 12:04 PM, Adrian Chadd wrote: > On 19 February 2014 11:59, Alexander Motin wrote: > >>> So if we're moving towards supporting (among others) a pcbgroup / RSS >>> hash style work load distribution across CPUs to minimise >>> per-connection lock contention, we really don't want the scheduler to >>> decide it can schedule things on other CPUs under enough pressure. >>> That'll just make things worse. >> True, though it is also not obvious that putting second thread on CPU run >> queue is better then executing it right now on another core. > Well, it depends if you're trying to optimise for "run all runnable > tasks as quickly as possible" or "run all runnable tasks in contexts > that minimise lock contention." > > The former sounds great as long as there's no real lock contention > going on. But as you add more chances for contention (something like > "100,000 concurrent TCP flows") then you may end up having your TCP > timer firing stuff interfere with more TXing or RXing on the same > connection. > > Chasing this stuff down is a pain, because it only really shows up > when you're doing lots of concurrency. > > I'm happy to make this a boot-time option and leave it off for the > time being. How's that? options THROUGHPUT Yes, looks like a latency vs throughput issue. One giant switch might be a starting point so that it doesn't become death of 1000 switches to get throughput or latency sensitive work done. > > > > -a > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >