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Date: Wed, 05 Nov 2003 17:04:22 +0800
From: David Xu <davidxu@viatech.com.cn>
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To: Jun Su <junsu@m-net.arbornet.org>
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cc: current@freebsd.org
Subject: Re: SYSENTER in FreeBSD
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Jun Su wrote:

>I noticed that Jeff Roberson implement this already. Is whi will be commit?
>http://kerneltrap.org/node/view/1531
>
>I google this because I found this feature is listed in the list of Kernel Improvement of WindowsXP. :-)
>
>Thanks,
>Jun Su
>
>  
>
I have almost done this experiment about 10 months ago.
http://people.freebsd.org/~davidxu/fastsyscall/
The patch is out of date and still not complete.
Also it can give you some performance improve, but I think too many 
things need to be changed,
and this really makes user ret code very dirty, some syscalls, for 
example, pipe() can not use
this fast syscall, becaues pipe() seems using two registers to return 
file handle, the performance gain
is immediately lost when the assemble code becomes more complex. I don't 
think this hack is worth
to do on IA32, I heard AMD has different way to support fast syscall, 
that may already in FreeBSD
AMD 64 branch.

David Xu