On Tue, Feb 17, 2009 at 10:01:13PM +0300, Vladislav Bolkhovitin wrote: > Vladislav Bolkhovitin, on 02/12/2009 09:35 PM wrote: >> Additional interesting observation is how badly simultaneous read IO >> streams are handled, if they aren't grouped in the corresponding IO >> contexts. In test 3 the result was as low as 4(!)MB/s. Wu, Jens, do you >> have any explanation on this? Why the inner tracks have so big >> preference? > > I realized, there is another explanation: access becomes about to be > completely random. I checked and it is true. Here is a sample "iostat -x > 3" output on the server: Yes it's all about 64K sized reads. Is this the stripe size of md0? Thanks, Fengguang > avg-cpu: %user %nice %system %iowait %steal %idle > 0.00 0.00 0.57 26.62 0.00 72.81 > > Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s > avgrq-sz avgqu-sz await svctm %util > sda 710.00 0.00 47.33 0.00 6058.67 0.00 128.00 > 0.12 2.59 2.51 11.87 > sdb 710.00 0.00 47.33 0.00 6058.67 0.00 128.00 > 3.99 84.34 21.13 100.00 > sdc 0.00 0.00 0.00 0.00 0.00 0.00 0.00 > 0.00 0.00 0.00 0.00 > sdc1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 > 0.00 0.00 0.00 0.00 > sdc2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 > 0.00 0.00 0.00 0.00 > md0 0.00 0.00 1514.67 0.00 12117.33 0.00 8.00 > 0.00 0.00 0.00 0.00 > dm-0 0.00 0.00 757.33 0.00 6058.67 0.00 8.00 > 32.87 43.41 1.32 100.00 > dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 > 0.00 0.00 0.00 0.00 > dm-2 0.00 0.00 757.33 0.00 6058.67 0.00 8.00 > 32.79 43.33 1.32 100.00 > > Thanks, > Vlad -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
