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Date: Mon, 27 Dec 2004 15:44:07 -0800
From: Ulrich Drepper <drepper@gmail.com>
Reply-To: Ulrich Drepper <drepper@gmail.com>
To: Brian Gerst <bgerst@didntduck.org>
Subject: Re: 2.4, 2.6, i686/athlon and LDT's
Cc: Arjan van de Ven <arjan@infradead.org>,
       Tymm Twillman <ttwillman@penguincomputing.com>,
       linux-kernel@vger.kernel.org
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On Mon, 27 Dec 2004 15:55:53 -0500, Brian Gerst <bgerst@didntduck.org> wrote:
> Using the LDT isn't inherently slower, since the cpu caches the segment
> descriptor regardless of if it came from the GDT or LDT.

Not using LDT's on 2.4 kernel other than RHEL3's means to have a
different ABI.  This is the /lib/libpthread.so.0 RH is shipping which
simply cannot be used in some/many situations since there is no
"thread register".  This means the programmer is not able to select
size and/or location of the stacks.  Interfaces like
pthread_attr_setstack() simply won't work at all.

So, do't confuse people with "does anyone have comparison information
w/threads using
LDT's and without (performance, protection, etc)?".  That's comparing
apples and oranges.