From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261987AbUL0V33 (ORCPT ); Mon, 27 Dec 2004 16:29:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261988AbUL0V32 (ORCPT ); Mon, 27 Dec 2004 16:29:28 -0500 Received: from canuck.infradead.org ([205.233.218.70]:15121 "EHLO canuck.infradead.org") by vger.kernel.org with ESMTP id S261987AbUL0V3Z (ORCPT ); Mon, 27 Dec 2004 16:29:25 -0500 Subject: Re: 2.4, 2.6, i686/athlon and LDT's From: Arjan van de Ven To: Brian Gerst Cc: Tymm Twillman , linux-kernel@vger.kernel.org In-Reply-To: <41D076D9.30404@didntduck.org> References: <41D0668B.206@penguincomputing.com> <1104178937.4187.16.camel@laptopd505.fenrus.org> <41D076D9.30404@didntduck.org> Content-Type: text/plain Date: Mon, 27 Dec 2004 22:29:17 +0100 Message-Id: <1104182957.4187.18.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 (2.0.2-3) Content-Transfer-Encoding: 7bit X-Spam-Score: 4.1 (++++) X-Spam-Report: SpamAssassin version 2.63 on canuck.infradead.org summary: Content analysis details: (4.1 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.3 RCVD_NUMERIC_HELO Received: contains a numeric HELO 1.1 RCVD_IN_DSBL RBL: Received via a relay in list.dsbl.org [] 2.5 RCVD_IN_DYNABLOCK RBL: Sent directly from dynamic IP address [80.57.133.107 listed in dnsbl.sorbs.net] 0.1 RCVD_IN_SORBS RBL: SORBS: sender is listed in SORBS [80.57.133.107 listed in dnsbl.sorbs.net] X-SRS-Rewrite: SMTP reverse-path rewritten from by canuck.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2004-12-27 at 15:55 -0500, Brian Gerst wrote: > Arjan van de Ven wrote: > > On Mon, 2004-12-27 at 11:46 -0800, Tymm Twillman wrote: > > > >>Hi all, > > > > > >>It appears that use of the LDT is to speed up context switching between > >>threads, although I haven't even found especially good references WRT > >>that. I have looked through the info in the IA Developers publications > >>and have whacked my head against Google quite a bit. However, every bit > >>of clarity I've found there has been offset by new confuzled bits. > > > > > > LDT's are *slow*. That's why glibc will try to avoid using them > > nowadays, and with 2.6 it won't; as for 2.4.. it depends if you use a > > vendor 2.4 it might be able to avoid using LDT's as well. > > Using the LDT isn't inherently slower, since the cpu caches the segment > descriptor regardless of if it came from the GDT or LDT. it does however increase context switch costs significantly since the LDT needs to be reloaded and reverified...