Re: Maxphys on -current?

[Brian Buhrow <buhrow%nfbcal.org@localhost>]

	hello.  Michael's e-mail explains the behavior I'm seeing with trying different block
sizes with NetBSD and FreeBSD.   
The scripts below show transfers of the same number of bytes using 1m and 64k block sizes for
NetBSD-9.99.77/amd64 and FreeBSD-13.1/amd64.  NetBSD is using SATA3 disks with NCQ enabled and
FreeBSD is using SATA3 disks with command queueing enabled.  The block size doesn't change the
speed of the transfers on either system.  Interestingly enough, however, the FreeBSD
performance is markedly worse on this test.  

-thanks
-Brian


NetBSD-99.77/amd64 with SATA3 disk
# dd if=/dev/rwd0a of=/dev/null bs=1m count=50000
50000+0 records in
50000+0 records out
52428800000 bytes transferred in 292.078 secs (179502735 bytes/sec)
# dd if=/dev/rwd0a of=/dev/null bs=65536 count=800000
800000+0 records in
800000+0 records out
52428800000 bytes transferred in 292.067 secs (179509496 bytes/sec)

FreeBSD-13.1/AMD64 with SATA3 disk
# dd if=/dev/da4 of=/dev/null bs=1m count=50000
50000+0 records in
50000+0 records out
52428800000 bytes transferred in 322.807433 secs (162415095 bytes/sec)
# dd if=/dev/da4 of=/dev/null bs=65536 count=800000
800000+0 records in
800000+0 records out
52428800000 bytes transferred in 322.433936 secs (162603232 bytes/sec)