From owner-freebsd-current Mon Jul 12 15: 1: 9 1999 Delivered-To: freebsd-current@freebsd.org Received: from herring.nlsystems.com (nlsys.demon.co.uk [158.152.125.33]) by hub.freebsd.org (Postfix) with ESMTP id 1FE731527D for ; Mon, 12 Jul 1999 15:01:03 -0700 (PDT) (envelope-from dfr@nlsystems.com) Received: from salmon.nlsystems.com (salmon.nlsystems.com [10.0.0.3]) by herring.nlsystems.com (8.9.3/8.8.8) with ESMTP id XAA02529; Mon, 12 Jul 1999 23:01:38 +0100 (BST) (envelope-from dfr@nlsystems.com) Date: Mon, 12 Jul 1999 23:01:38 +0100 (BST) From: Doug Rabson To: Matthew Dillon Cc: Poul-Henning Kamp , Luoqi Chen , jeremyp@gsmx07.alcatel.com.au, freebsd-current@FreeBSD.ORG, mike@ducky.net Subject: Re: Ack! Wrong results. In-Reply-To: <199907121812.LAA70732@apollo.backplane.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Mon, 12 Jul 1999, Matthew Dillon wrote: > How did that happen?!!! Argg.. I didn't save the email. > > Here are better results: > > Empty loop: > > mode 0 9.21 ns/loop nproc=1 lcks=EMPTY > > With and without lock prefix, one and two processes > > mode 1 16.48 ns/loop nproc=1 lcks=no > mode 2 23.65 ns/loop nproc=2 lcks=no > mode 3 93.02 ns/loop nproc=1 lcks=yes > mode 4 160.82 ns/loop nproc=2 lcks=yes > > With and without lock prefix, one and two processes, with > other global memory operations (note that the lock prefix instructions > have absorbed the other memory ops) > > mode 5 37.64 ns/loop nproc=1 lcks=no > mode 6 89.28 ns/loop nproc=2 lcks=no > mode 7 88.32 ns/loop nproc=1 lcks=yes > mode 8 161.08 ns/loop nproc=2 lcks=yes > > My conclusion from this is that the lock protocols have a general case > overhead of 50 to 80 nS on a duel P-III/450 system. I don't think it > would be noticeable. Just as another data point, it would be interesting to see the overhead for non-inline versions (i.e. functions in the kernel which are using lock or not called by code in loaded modules). The alpha versions of these operations are already non-inline since it takes quite a few instructions to implement them. -- Doug Rabson Mail: dfr@nlsystems.com Nonlinear Systems Ltd. Phone: +44 181 442 9037 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message