Re: Performance riddle: mounted fs much faster than dev

[David Holland <dholland-tech%netbsd.org@localhost>]

On Mon, May 26, 2014 at 10:11:16PM +0200, Thomas Schmitt wrote:
 >   netbsd# dd bs=2048 count=131072 if=/dev/wd1f of=/dev/null

The short answer is: use rwd1f, not wd1f. The latter goes through the
buffer cache, but unlike when you mount it uses the old (non-unified)
buffer cache for everything... this is not the same and it won't
perform the same, and it's also not really that surprising that it
performs badly.

It is probable that the block and character device nodes for disks
should be folded together, as at this point the block devices really
can't/shouldn't be used for anything except mount. However, this is a
Big Deal (TM) and probably won't happen anytime soon.

-- 
David A. Holland
dholland%netbsd.org@localhost