From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263573AbTLNJk6 (ORCPT ); Sun, 14 Dec 2003 04:40:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263661AbTLNJk6 (ORCPT ); Sun, 14 Dec 2003 04:40:58 -0500 Received: from mail-06.iinet.net.au ([203.59.3.38]:38569 "HELO mail.iinet.net.au") by vger.kernel.org with SMTP id S263573AbTLNJk4 (ORCPT ); Sun, 14 Dec 2003 04:40:56 -0500 Message-ID: <3FDC3023.9030708@cyberone.com.au> Date: Sun, 14 Dec 2003 20:40:51 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030827 Debian/1.4-3 X-Accept-Language: en MIME-Version: 1.0 To: Jamie Lokier CC: bill davidsen , linux-kernel@vger.kernel.org Subject: Re: [CFT][RFC] HT scheduler References: <20031213022038.300B22C2C1@lists.samba.org> <3FDAB517.4000309@cyberone.com.au> <3FDBC876.3020603@cyberone.com.au> <20031214043245.GC21241@mail.shareable.org> In-Reply-To: <20031214043245.GC21241@mail.shareable.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jamie Lokier wrote: >Nick Piggin wrote: > >>>Shared runqueues sound like a simplification to describe execution units >>>which have shared resourses and null cost of changing units. You can do >>>that by having a domain which behaved like that, but a shared runqueue >>>sounds better because it would eliminate the cost of even considering >>>moving a process from one sibling to another. >>> >>You are correct, however it would be a miniscule cost advantage, >>possibly outweighed by the shared lock, and overhead of more >>changing of CPUs (I'm sure there would be some cost). >> > >Regarding the overhead of the shared runqueue lock: > >Is the "lock" prefix actually required for locking between x86 >siblings which share the same L1 cache? > That lock is still taken by other CPUs as well for eg. wakeups, balancing, and so forth. I guess it could be a very specific optimisation for spinlocks in general if there was only one HT core. Don't know if it would be worthwhile though.