Date: Sun, 14 Apr 1996 13:46:21 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: peter@nmti.com (Peter da Silva) Cc: hackers@freebsd.org Subject: Re: Pentium fast copy? Message-ID: <199604140416.NAA11976@genesis.atrad.adelaide.edu.au> In-Reply-To: <9604140152.AA14757@sonic.nmti.com.nmti.com> from "Peter da Silva" at Apr 13, 96 08:52:50 pm
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Peter da Silva stands accused of saying: > > The following quote from a paper (sorry, I don't know what the paper is > offhand) appeared on the Firewalls mailing list. What's FreeBSD like on > this front? > > Our results show that none of the systems adequately delivers the > Pentium's memory write performance. For example, the Pentium can > copy data at over 160 megabytes/second using a prefetching copy > routine, yet none of the systems we tested have implemented such a > routine. As described below, the prefetching routines address the > fact that the Pentium does not have a write-allocate cache. > Without this optimization, the same routines copy data at about 40 > megabytes/second. Most of the implementations that have been thrown around here tend to average at about 40M/sec. There have been some significantly faster under certain specialised circumstances, but they tend to perform poorly on older processors, or they fall foul of some of the caching policies imposed by some motherboards, or they impose extra overhead elsewhere in the system (the most common complaint is that context-switches have to become more complex to handle the technique). I'd be really interested to see what sort of hardware they're using that has 160M/sec of memory bandwidth. Unless they're running 100% static RAM, I suspect they've never actually implemented their code on a practical scale 8( -- ]] Mike Smith, Software Engineer msmith@atrad.adelaide.edu.au [[ ]] Genesis Software genesis@atrad.adelaide.edu.au [[ ]] High-speed data acquisition and (GSM mobile) 0411-222-496 [[ ]] realtime instrument control (ph/fax) +61-8-267-3039 [[ ]] Collector of old Unix hardware. "Where are your PEZ?" The Tick [[
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