cvs commit: src/sys/geom/zero g_zero.c src/sys/modules/geom/geom_zero Makefile

Pawel Jakub Dawidek pjd at
Mon Jul 25 10:47:01 GMT 2005

On Mon, Jul 25, 2005 at 07:44:57PM +0930, Daniel O'Connor wrote:
+> On Monday 25 July 2005 19:33, Pawel Jakub Dawidek wrote:
+> >   Add a very simple and small GEOM class - ZERO.
+> >   It creates very huge provider (41PB) /dev/gzero.
+> >   On BIO_READ request it zero-fills bio_data and on BIO_WRITE it does
+> > nothing. You can also set sysctl to 0 to do nothing
+> > even for BIO_READ.
+> >
+> >   I'm using it for performance testing where it is very helpful.
+> How long does a newfs take on that?

You will not be able to newfs this actually, but you can do other
interesting tests like:

- GEOM throughput:

	# dd if=/dev/gzero of=/dev/null bs=1m count=10000

- Overhead when adding more levels:

	# gnop gzero
	# gnop gzero.nop
	# gnop gzero.nop.nop
	# gnop gzero.nop.nop.nop
	# gnop gzero.nop.nop.nop.nop
	# dd if=/dev/gzero of=/dev/null bs=1m count=10000
	# dd if=/dev/gzero.nop.nop.nop.nop.nop of=/dev/null bs=1m count=10000

- Test performance of various classes.

And much more:)

Pawel Jakub Dawidek             
pjd at                 
FreeBSD committer                         Am I Evil? Yes, I Am!
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