Date: Fri, 5 Apr 1996 12:56:29 +0100 (BST) From: Paul Richards <paul@originat.demon.co.uk> To: davidg@Root.COM Cc: asami@cs.berkeley.edu, current@FreeBSD.org, nisha@cs.berkeley.edu, tege@matematik.su.se, hasty@rah.star-gate.com Subject: Re: fast memory copy for large data sizes Message-ID: <199604051156.MAA00692@originat.demon.co.uk> In-Reply-To: <199604051021.CAA00222@Root.COM> from "David Greenman" at Apr 5, 96 02:21:48 am
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In reply to David Greenman who said > > size libc ours > > 32 15.258789 MB/s 6.103516 MB/s > > 64 20.345052 MB/s 15.258789 MB/s > > 128 17.438616 MB/s 15.258789 MB/s > > This would be a big lose in the kernel since just about all bcopy's fall > into this range _except_ disk I/O block copies. I know this can be done better > using other techniques (non-FP, see hackers mail from about 3 months ago). You > should talk to John Dyson who's also working on this. A quick check of the size would probably help and use the original method for small copies. Run a benchmark on such a scheme and see what happens. Anyway, I had another thought, do we save the fp registers across context switches? I seem to remember that we don't always and instead save them when something tries to do FP operations, I might be imagining this but if it's true increased use of the fp regs is going to impact context switching. -- Paul Richards, Originative Solutions Ltd. Internet: paul@netcraft.co.uk, http://www.netcraft.co.uk Phone: 0370 462071 (Mobile), +44 1225 447500 (work)
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