Previously, Jiri Kristek wrote in comp.os.qnx:
we intend to write large volume of data directly to disk via device
(/dev/hd1) bypassing the file system. We tested maximal transfer rates for
EIDE disks and the results are very poor for QNX4.25 as well as for Neutrino
2.1. We did not succeeded to get over 5MB/sec for block read and 3MB/sec for
block write. Parameters for used disk drivers tells about 15MB/sec or
higher. The results for Neutrino are a little worse than for QNX4.25 in PIO
modes and about 40% worse in DMA mode.
Any comments ???
Is there a possibility to run EIDE drivers for QNX4.25 in DMA mode?
To bypass Fsys entirely, you might try using Blkfsys. The reason to
try this is that Fsys caches direct i/o through /dev/hd#, whereas
Blkfsys does not. This might create a problem accessing /dev/hd0
as a file system. I once solved this problem in a kludge manner by
creating a psuedo driver that read /dev/hd0 directly. This driver
was owned by Fsys, which was therefore requesting blocks through
Blkfsys. There is some overhead in this process, but it allows
direct I/O of /dev/hd1 through Blkfsys.
You also could try to write your own DMA mode driver for EIDE.
Mitchell Schoenbrun --------- maschoen@pobox.com
