low(er) disk performance with sched_4bsd then with sched_ule

Hi,

I've a dual-cpu system (SMP) which runs with 2 PIII-850 MHz on an Intel
Serverboard (440GX chipset). My diskspace is provided by a RAID-5
containing 4 WD2500KS harddrives connected to a 3ware 9500S-4LP
controller which runs at 32bit/33MHz.
The system itself runs FreeBSD 6.0-BETA2.

with SCHED_4BSD in the kernel:

root_at_nudel olivleh1> dd if=/dev/zero of=/mnt/files/test.dd bs=64k count=32000
32000+0 records in
32000+0 records out
2097152000 bytes transferred in 44.136711 secs (47514913 bytes/sec)

with SCHED_ULE in the kernel:

root_at_nudel olivleh1> dd if=/dev/zero of=/mnt/files/test.dd bs=64k count=32000
32000+0 records in
32000+0 records out
2097152000 bytes transferred in 27.005334 secs (77656954 bytes/sec)

the scheduler is the only difference between both configs - everything
else is the same. Kernel debugging is disabled, malloc.conf exists.

Filesystem                    Size    Used   Avail Capacity  Mounted on
/dev/da0s1a                   496M    159M    297M    35%    /
devfs                         1.0K    1.0K      0B   100%    /dev
/dev/da0s1d                   496M     20M    436M     4%    /var
/dev/da0s1e                   496M     22M    434M     5%    /tmp
/dev/da0s1f                    19G    2.9G     15G    16%    /usr
/dev/da0s1g                   671G    216G    455G    32%    /mnt/files


3ware device driver for 9000 series storage controllers, version: 3.60.00.017
twa0: <3ware 9000 series Storage Controller> port 0x3400-0x34ff mem 0xf4102800-0xf41028ff,0xf4800000-0xf4ffffff irq 16 at device 16.0 on pci0
twa0: [FAST]
twa0: INFO: (0x15: 0x1300): Controller details:: 4 ports, Firmware FE9X 2.08.00.005, BIOS BE9X 2.03.01.052

da0 at twa0 bus 0 target 0 lun 0
da0: <AMCC 9500S-4LP  DISK 2.08> Fixed Direct Access SCSI-3 device 
da0: 100.000MB/s transfers
da0: 715224MB (1464778752 512 byte sectors: 255H 63S/T 91178C)


Any idea where the 30MB/sec drawback comes from and if I missed sth.?
I mean why there are 30MB/s more or less is worth to think about imho.

-- 
 Oliver Lehmann
  http://www.pofo.de/
  http://wishlist.ans-netz.de/