On Thu, Jul 21, 2011 at 3:35 PM, Freddie Cash <fjwc...@gmail.com> wrote:
> On Mon, Jul 18, 2011 at 7:06 PM, Matthew Dillon < > dil...@apollo.backplane.com> wrote: > >> Ok, well this is interesting. Basically it comes down to whether we >> want to starve read operations or whether we want to starve write >> operations. >> >> The FreeBSD results starve read operations, while the DragonFly results >> starve write operations. That's the entirety of the difference between >> the two tests. >> >> Would using the disk scheduler's in FBSD/DFly help with this at all? > > FreeBSD includes a geom_sched class for enabling pluggable disk scheduler's > (currently only round-robin algorithm is implemented). > http://info.iet.unipi.it/~luigi/geom_sched/ > > Page 39 of the presentation on GEOM_SCHED shows the following, indicating that it should make a big difference in the blogbench results (note the second result with greedy read and write): Some preliminary results on scheduler’s performance in some easy cases (the focus here is on the framework). Measurement is using multiple dd instances on a filesystems, all speeds in MiB/s. two greedy readers, throughput improvement NORMAL: 6.8 + 6.8 ; GSCHED RR: 27.0 + 27.0 one greedy reader, one greedy writer, capture effect NORMAL: R: 0.234 W:72.3 ; GSCHED RR: R:12.0 W:40.0 multiple greedy writers, only small loss of througput NORMAL: 16+16; RR: 15.5 + 15.5 one sequential reader, one random reader (fio) NORMAL: Seq: 4.2 Rand: 4.2; RR: Seq: 30 Rand: 4.4 > And I believe DFly has dsched? > > >> This is all with swapcache turned off. The only way to test in a >> fair manner with swapcache turned on (with a SSD) is if the FreeBSD >> test used a similar setup w/ZFS. >> >> ZFS includes it's own disk scheduler, so geom_sched wouldn't help in that > case. Would be interesting to see a comparison of HAMMER+swapcache and > ZFS+L2ARC, though. > > -- > Freddie Cash > fjwc...@gmail.com > -- Freddie Cash fjwc...@gmail.com
