Date: Mon, 12 Jul 1999 23:01:38 +0100 (BST) From: Doug Rabson <dfr@nlsystems.com> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Poul-Henning Kamp <phk@critter.freebsd.dk>, Luoqi Chen <luoqi@watermarkgroup.com>, jeremyp@gsmx07.alcatel.com.au, freebsd-current@FreeBSD.ORG, mike@ducky.net Subject: Re: Ack! Wrong results. Message-ID: <Pine.BSF.4.10.9907122259540.58023-100000@salmon.nlsystems.com> In-Reply-To: <199907121812.LAA70732@apollo.backplane.com>
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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
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