well i'm performing a large number of port accesses since the data gets transferred bit-by-bit over a single parallel port pin with another pin acting as clock. so transfering 256 kbyte of data means i'm doing >= 256*1024*8*2 ioctls. i guess when transfering data on a nibble, byte, word or dword basis the overhead isn't that dramatic.
alex John Baldwin schrieb am 2009-07-24: > On Friday 24 July 2009 6:42:34 am Alexander Best wrote: > > thanks for the hint. > > if spent a bit of time and turned the in/out opcodes to ppi ioctls. > > actually > i > > was very surprised about the results since you said the overhead > > wouldn't be > > that big. > > uploading a 256 kbyte file i got the following results: > > using ppi: 17.120 seconds > > using in/out opcodes: 8.001 seconds > > so i think i'll rather stick to my old inline assembly code even if > > it can't > > be considered nice programming style, but the ppi overhead isn't > > something i > > can cope with in my app. > Hmmm, that is a bit much. Though I do suppose you are incurring a > user -> > kernel -> user transition for each I/O access. _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
