Date: Fri, 26 Jan 2007 18:03:27 +0100 From: Hans Petter Selasky <hselasky@c2i.net> To: freebsd-current@freebsd.org Cc: cperciva@freebsd.org, "M. Warner Losh" <imp@bsdimp.com>, current@freebsd.org Subject: Re: Interesting speed benchmarks Message-ID: <200701261803.28024.hselasky@c2i.net> In-Reply-To: <20070126.092842.1973603551.imp@bsdimp.com> References: <45B9895B.9020709@freebsd.org> <45B99A59.6070902@freebsd.org> <20070126.092842.1973603551.imp@bsdimp.com>
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On Friday 26 January 2007 17:28, M. Warner Losh wrote: > In message: <45B99A59.6070902@freebsd.org> > > Colin Percival <cperciva@freebsd.org> writes: > : M. Warner Losh wrote: > : > In message: <45B9895B.9020709@freebsd.org> > : > > : > Colin Percival <cperciva@freebsd.org> writes: > : > : M. Warner Losh wrote: > : > : > Firewire does around 40MB/s, while USB 2.0 maxes out at about > : > : > 12MB/s. > : > : > : > : I get 25MB/s from my Vantec Nexstar3 > : > : USB 2.0 enclosure: > : > : > : > : http://www.daemonology.net/blog/2006-01-28-vantex-nexstar3.html > : > > : > Still, 25MB/s is no 40MB/s... > : > : Sure, but it means that the performance issues aren't simply a global > : "USB 2.0 is bad". What does `diskinfo -c` say about your firewire and > : USB interfaces? > > > I haven't tested the Hans Petter Selasky usb stack to see if it is any > better. It appears there's no scatter gather there, so that might > make the numbers even worse. But if the command queueing is better, > then it might make up for it. Yes, it has scatter and gather since August last year :-) But all USB drivers currently use copy-in/copy-out to/from the DMA buffer. With regard to "umass" there is one copy-out/copy-in per transfer. Currently all transfers are done in bulks of 131072 bytes, so there is not too much overhead. I am considering direct buffer loading. --HPS
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