From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261982AbUL0Uzt (ORCPT ); Mon, 27 Dec 2004 15:55:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261984AbUL0Uzs (ORCPT ); Mon, 27 Dec 2004 15:55:48 -0500 Received: from quark.didntduck.org ([69.55.226.66]:29121 "EHLO quark.didntduck.org") by vger.kernel.org with ESMTP id S261982AbUL0Uzo (ORCPT ); Mon, 27 Dec 2004 15:55:44 -0500 Message-ID: <41D076D9.30404@didntduck.org> Date: Mon, 27 Dec 2004 15:55:53 -0500 From: Brian Gerst User-Agent: Mozilla Thunderbird 1.0 (Windows/20041206) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Arjan van de Ven CC: Tymm Twillman , linux-kernel@vger.kernel.org Subject: Re: 2.4, 2.6, i686/athlon and LDT's References: <41D0668B.206@penguincomputing.com> <1104178937.4187.16.camel@laptopd505.fenrus.org> In-Reply-To: <1104178937.4187.16.camel@laptopd505.fenrus.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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. Using an LDT however consumes kernel memory, which can slow down the system from memory pressure if you have many processes/threads using them. -- Brian Gerst