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Date: 22 Aug 2004 16:23:44 +0200
Date: Sun, 22 Aug 2004 16:23:44 +0200
From: Andi Kleen <ak@muc.de>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, eich@suse.de
Subject: Re: [patch] context-switching overhead in X, ioport(), 2.6.8.1
Message-ID: <20040822142344.GA81458@muc.de>
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> Xorg and XFree assume the kernel will have intelligent limits. When the
> range went up the EnableIO code in turn switched to ioperm.

Which was the wrong thing to do since it is slower.

> 
> The actual code is:
> 
>        if (ioperm(0, 1024, 1) || iopl(3))
>                 FatalError("xf86EnableIOPorts: Failed to set IOPL for
> I/O\n")
> 
> (os-support/linux/lnx_video.c:xf86EnableIO)
> 
> Flip those around and rebuild.

It would be better to do that in the official release.

-Andi