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From: ast@cs.vu.nl (Andy Tanenbaum)
Newsgroups: comp.unix.wizards,comp.os.misc
Subject: Re: Reducing system calls overhead
Message-ID: <1316@ast.cs.vu.nl>
Date: 28 Aug 88 20:06:40 GMT
References: <21606@ccicpg.UUCP>
Reply-To: ast@cs.vu.nl (Andy Tanenbaum)
Organization: VU Informatica, Amsterdam
Lines: 12

In article <21606@ccicpg.UUCP> goshen@ccicpg.UUCP (Shmuel Goshen) writes:
>I have been looking recently at ways to reduce the system call overhead.

I would suggest you look closely at MULTICS and OS/2, which uses many ideas
taken straight from MULTICS.  In these systems, the entire operating system is
contained within the address space of each user process, with appropriate
protection mechanisms to keep users from doing naughty things.  As a result,
a system call is just a procedure call to an operating system routine, and the
complete overhead is only slightly more than a normal procedure call.  This
gets the time down from milliseconds to microseconds.  

Andy Tanenbaum (ast@cs.vu.nl)