Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751306AbXBNMUH (ORCPT ); Wed, 14 Feb 2007 07:20:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751318AbXBNMUH (ORCPT ); Wed, 14 Feb 2007 07:20:07 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:56844 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751306AbXBNMUF (ORCPT ); Wed, 14 Feb 2007 07:20:05 -0500 Date: Wed, 14 Feb 2007 13:17:00 +0100 From: Pavel Machek To: Bill Davidsen Cc: Jakub Jelinek , Arjan van de Ven , linux-kernel@vger.kernel.org Subject: Re: [ANN] Userspace M-on-N threading model implementation. Alpha release. Message-ID: <20070214121700.GB23857@elf.ucw.cz> References: <66910A579C9312469A7DF9ADB54A8B7D5C2B90@exchange.ZeugmaSystems.local> <45C362D2.2040407@tmr.com> <1170516376.3073.1015.camel@laptopd505.fenrus.org> <45C63E30.4010106@tmr.com> <20070204202053.GC20307@devserv.devel.redhat.com> <45C65353.5000602@tmr.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45C65353.5000602@tmr.com> 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: 1250 Lines: 31 Hi! > >>How does that work? Switching between kernel threads requires going into > >>the kernel, user level thread switches are all done in user mode. > >> > >>Do you have some way to change o/s threads w/o going into the kernel? > >> > > > >But going into kernel is not very expensive on Linux. > > > >On the other side, the overhead you need to add for every single syscall > >that might block for the M:N threads and the associated complications > >which make it far harder to conform to POSIX IMHO far outweight the costs > >of going into the kernel for a context switch. > > That really wasn't my question, Arjan said that switching real threads > wasn't a context switch in the hardware sense, and I was asking if I > missed something. It may be cheap, but it would seem to be a context > switch none-the-less. It is not reloading %cr3. 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/