From owner-freebsd-hackers Fri Oct 20 13:36:39 1995 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.6.12/8.6.6) id NAA18575 for hackers-outgoing; Fri, 20 Oct 1995 13:36:39 -0700 Received: from phaeton.artisoft.com (phaeton.Artisoft.COM [198.17.250.211]) by freefall.freebsd.org (8.6.12/8.6.6) with ESMTP id NAA18568 for ; Fri, 20 Oct 1995 13:36:32 -0700 Received: (from terry@localhost) by phaeton.artisoft.com (8.6.11/8.6.9) id NAA05261; Fri, 20 Oct 1995 13:28:10 -0700 From: Terry Lambert Message-Id: <199510202028.NAA05261@phaeton.artisoft.com> Subject: Re: NetBSD/FreeBSD (pthreads) To: leisner@sdsp.mc.xerox.com (Marty Leisner) Date: Fri, 20 Oct 1995 13:28:10 -0700 (MST) Cc: cimaxp1!jb@werple.net.au, leisner@sdsp.mc.xerox.com, hackers@FreeBSD.ORG, jb@cimlogic.com.au In-Reply-To: <9510201855.AA17636@gnu.mc.xerox.com> from "Marty Leisner" at Oct 20, 95 11:55:04 am X-Mailer: ELM [version 2.4 PL24] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Content-Length: 1038 Sender: owner-hackers@FreeBSD.ORG Precedence: bulk > Why would I want kernel level threads? > > 1) does a debugger understand userlevel threads? > 2) if I run a threaded application under strace, with kernel > levels threads is may make some sense...with user level threads > there's all this junk in the way... > 3) Anyone have good hard numbers about the differences between user/kernel > level threads on performance? Yeah. On an 8 processor box, a kernel-threaded app is 8 times as concurrent as a user threaded app (which by definition can only utilize one processor at a time). Consider also that thengs like statfs/fstatfs are potentially long-blocking operations that aren't select()'able. Debugging tools are another (almost completely unrelated) problem. > Like I said, the mit package is awfully clever... So's the AT&T/Sun stuff. The problem is that no one has bothered with implementing both types of clever in the same package. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.