jonathan f7bd3a0119 Move existing contextsw-avoidance code in rzdump() earlier, since rzready()
also calls biowait().

Some drives seek to modepage on every modepage geometry-sense in rzready()
cache dev_t of last readied device in rzdump() to elide rzready() calls.
2x speedup of dumps on rz25 and 20x-30x speedup on some IBM OEM 4gig drives.
1998-02-21 20:20:55 +00:00
..