Message-ID: <1040308834.3e01da62a8761@209.51.155.18>
Date: Thu, 19 Dec 2002 09:40:34 -0500
From: billyrose@billyrose.net
To: root@chaos.analogic.com
Cc: linux-kernel@vger.kernel.org
Subject: Re: Intel P6 vs P7 system call performance
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Richard B. Johnson wrote:

> The target, i.e., the label 'goto' would be the reserved page for the
> system call. The whole purpose was to minimize the number of CPU cycles
> necessary to call 0xfffff000 and return. The system call does not have
> issue a 'far' return, it can do anything it requires. The page at
> 0xfffff000 is mapped into every process and is in that process CS space
> already.

that being the case, why push %cs and reload it without reason as the
code is mapped into every process?

therefore, would it not suffice to use:

        ...
        long_call(); //call to $0xfffff000 via near ret
        //code at $0xfffff000 returns directly here when a ret is issued
        ...

long_call:
        pushl $0xfffff000
        ret

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