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Re: I/O permission control in OSKit-Mach

From: Adam Olsen
Subject: Re: I/O permission control in OSKit-Mach
Date: Tue, 16 Oct 2001 05:48:02 +0000
User-agent: Mutt/1.3.20i

On Tue, Oct 16, 2001 at 04:16:42AM +0200, Marcus Brinkmann wrote:
> A task requesting some I/O permission will get a full blown 8192 bytes large
> bitmap, which is copied in the processor TSS at every switch to the task.
> (Linux by default only uses a half bitmap, and provides a full one at
> request by calling a special function -- not ideal either, interface-wise).

Given how expensive copying 8192 bytes is bound to be, wouldn't it be
cheaper to break the bitmap up into segments, and when switching only
set the necesary parts?  (either zero the old ones and load the new
ones, or zero the old ones not used in the new one and load the common
ones.)  This'd probably be worse for everything that uses over half a
bitmap, but I have a feeling most usages will only be a small

Adam Olsen, aka Rhamphoryncus

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