Date: Wed, 14 Sep 2005 12:38:47 -0600 From: Scott Long <scottl@samsco.org> To: Oliver Lehmann <lehmann@ans-netz.de> Cc: current@freebsd.org Subject: Re: low(er) disk performance with sched_4bsd then with sched_ule Message-ID: <43286E37.40203@samsco.org> In-Reply-To: <20050914194612.15692485.lehmann@ans-netz.de> References: <20050914194612.15692485.lehmann@ans-netz.de>
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Oliver Lehmann wrote: > 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@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@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. > Indeed. This definitely warrants much more testing and investigation. My best guess is that ULE is allowing the uio copies of the data between kernel and userland to complete with fewer interruptions. It could also be better about keeping the threads from ping-ponging between CPUs. Can you retest with different block sizes, ranging from 4k to 1m? Scott
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