Date: Mon, 5 Jun 2006 11:42:59 -0400 (EDT) From: Garrett Wollman <wollman@khavrinen.csail.mit.edu> To: rwatson@freebsd.org Cc: , arch@freebsd.org Subject: Re: Why use `thread' as an argument of Syscalls? Message-ID: <200606051542.k55Fgx9V079169@khavrinen.csail.mit.edu> In-Reply-To: <20060605163559.N50057@fledge.watson.org> References: <1fa17f810606050044k2847e4a2i150eb934ed84006f@mail.gmail.com> <Pine.GSO.4.64.0606050744190.13542@sea.ntplx.net> <1fa17f810606050608l5bd2ec5ch37663375f6fa5b64@mail.gmail.com> <Pine.GSO.4.64.0606051118180.14745@sea.ntplx.net>
next in thread | previous in thread | raw e-mail | index | archive | help
Robert Watson writes: >Certainly consistency. Most system calls do actually use the argument at some >point -- be it to look up a file descriptor, access control, or the like, and >the calling context has it for free and in-hand anyway. I believe it was the intention of the 4.4BSD developers to completely eliminate "curproc" (as they had already successfully eliminated "u"), on the theory that with a modern (RISC) processor architecture, passing the current process as a parameter wouldn't cost anything (since it would stay in a register for the life of the system call) whereas making a context-switched "curproc" would be expensive. -GAWollman
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200606051542.k55Fgx9V079169>