Presumably it's going faster when you have a deeper iodepth? So the reason it's using more CPU is because it's doing more work. That's all there is to it. (And the OSD uses a lot more CPU than some storage systems do, because it does a lot more work than them.) -Greg
On Thursday, September 11, 2014, yuelongguang <fasts...@163.com> wrote: > hi,all > i am testing rbd performance, now there is only one vm which is using > rbd as its disk, and inside it fio is doing r/w. > the big diffenence is that i set a big iodepth other than iodepth=1. > according to my test, the bigger iodepth, the bigger cpu usage. > > analyse the output of top command. > 1. > 12% wa, if it means disk speed is not fast enough? > > 2. from where we can know whether ceph's number of threads is enough > or not? > > > how do you think about it, which part is using up cpu? i want to find the > root cause, why big iodepth leads to high cpu usage. > > > ---default options---- > osd_op_threads": "2", > "osd_disk_threads": "1", > "osd_recovery_threads": "1", > "filestore_op_threads": "2", > > > thanks > > ----------top---------------iodepth=16----------------- > top - 15:27:34 up 2 days, 6:03, 2 users, load average: 0.49, 0.56, 0.62 > Tasks: 97 total, 1 running, 96 sleeping, 0 stopped, 0 zombie > Cpu(s): 19.0%us, 8.1%sy, 0.0%ni, 59.3%id, 12.1%wa, 0.0%hi, 0.8%si, > 0.7%st > Mem: 1922540k total, 1853180k used, 69360k free, 7012k buffers > Swap: 1048568k total, 76796k used, 971772k free, 1034272k cached > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ > COMMAND > > 2763 root 20 0 1112m 386m 5028 S 60.8 20.6 200:43.47 ceph-osd > > -------------top-------------------------------------------- > top - 19:50:08 up 1 day, 10:26, 2 users, load average: 1.55, 0.97, 0.81 > Tasks: 97 total, 1 running, 96 sleeping, 0 stopped, 0 zombie > Cpu(s): 37.6%us, 14.2%sy, 0.0%ni, 37.0%id, 9.4%wa, 0.0%hi, 1.3%si, > 0.5%st > Mem: 1922540k total, 1820196k used, 102344k free, 23100k buffers > Swap: 1048568k total, 91724k used, 956844k free, 1052292k cached > > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ > COMMAND > > 4312 root 20 0 1100m 337m 5192 S 107.3 18.0 88:33.27 > ceph-osd > > 1704 root 20 0 514m 272m 3648 S 0.7 14.5 3:27.19 ceph-mon > > > > --------------iostat------------------ > > Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz > avgqu-sz await svctm %util > vdd 5.50 137.50 247.00 782.00 2896.00 8773.00 > 11.34 7.08 3.55 0.63 65.05 > > Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz > avgqu-sz await svctm %util > vdd 9.50 119.00 327.50 458.50 3940.00 4733.50 > 11.03 12.03 19.66 0.70 55.40 > > Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz > avgqu-sz await svctm %util > vdd 15.50 10.50 324.00 559.50 3784.00 3398.00 > 8.13 1.98 2.22 0.81 71.25 > > Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz > avgqu-sz await svctm %util > vdd 4.50 253.50 273.50 803.00 3056.00 12155.00 > 14.13 4.70 4.32 0.55 59.55 > > Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz > avgqu-sz await svctm %util > vdd 10.00 6.00 294.00 488.00 3200.00 2933.50 > 7.84 1.10 1.49 0.70 54.85 > > Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz > avgqu-sz await svctm %util > vdd 10.00 14.00 333.00 645.00 3780.00 3846.00 > 7.80 2.13 2.15 0.90 87.55 > > Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz > avgqu-sz await svctm %util > vdd 11.00 240.50 259.00 579.00 3144.00 10035.50 > 15.73 8.51 10.18 0.84 70.20 > > Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz > avgqu-sz await svctm %util > vdd 10.50 17.00 318.50 707.00 3876.00 4084.50 > 7.76 1.32 1.30 0.61 62.65 > > Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz > avgqu-sz await svctm %util > vdd 4.50 208.00 233.50 918.00 2648.00 19214.50 > 18.99 5.43 4.71 0.55 63.20 > > Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz > avgqu-sz await svctm %util > vdd 7.00 1.50 306.00 212.00 3376.00 2176.50 > 10.72 1.03 1.83 0.96 49.70 > > > > > -- Software Engineer #42 @ http://inktank.com | http://ceph.com
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