Re: Interesting speed benchmarks

On Friday 26 January 2007 17:28, M. Warner Losh wrote:
In message: <45B99A59.6070902@xxxxxxxxxxx>

Colin Percival <cperciva@xxxxxxxxxxx> writes:
: M. Warner Losh wrote:
: > In message: <45B9895B.9020709@xxxxxxxxxxx>
: >
: > Colin Percival <cperciva@xxxxxxxxxxx> 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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