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Date:      Mon, 7 Dec 1998 11:12:06 +0100
From:      Martin Cracauer <cracauer@cons.org>
To:        Brett Glass <brett@lariat.org>, chat@FreeBSD.ORG
Subject:   Re: Question regarding Linux emulation
Message-ID:  <19981207111206.A20322@cons.org>
In-Reply-To: <4.1.19981206215315.042becc0@127.0.0.1>; from Brett Glass on Sun, Dec 06, 1998 at 09:53:49PM -0700
References:  <4.1.19981206215315.042becc0@127.0.0.1>

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In <4.1.19981206215315.042becc0@127.0.0.1>, Brett Glass wrote: 
> I was asked these questions this evening, and don't know the answers.
> 
> How much of a speed penalty, if any, is incurred for using Linux emulation
> under FreeBSD compared to running a natively compiled version of the same
> program (or, for that matter, running the Linux program under Linux)? How
> "thin" is the Linux emulation layer? What calls can be expected to incur a
> substantial penalty due to translation of data structures, emulation of
> system facilities, etc.?

The emulation is mostly just an additional function call and a very
short code path to map some table to another (unually the same :-) or
to rebuild function arguments, often structs. Even signal delivery
code is quite small.

Remember that this is only done for system calls and a minimal system
call - emulated or not - is so costly in itself that this little extra
CPU stuff is unnoticeable.

Martin
-- 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Martin Cracauer <cracauer@cons.org> http://www.cons.org/cracauer
BSD User Group Hamburg, Germany     http://www.bsdhh.org/

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