There are some hints in https://wiki.openstack.org/wiki/Documentation/HypervisorTuningGuide

There are some tips in https://www.linux-kvm.org/page/Tuning_KVM too but you’d need to find the corresponding OpenStack flags on the guest/images/hosts/flavors.

Overall, there are several options so it’s recommended to establish a baseline performance on a representative work load and try the various options.

Tim

From: Manuel Sopena Ballesteros <manuel.sb@garvan.org.au>
Date: Wednesday, 1 May 2019 at 06:35
To: "openstack-discuss@lists.openstack.org" <openstack-discuss@lists.openstack.org>
Subject: how to get best io performance from my block devices

Dear Openstack community,

I would like to have a high performance distributed database running in Openstack vms. I tried attaching dedicated nvme pci devices to the vm but the performance is not as good as I can get from bare metal.

Bare metal:

[root@zeus-54 data]# fio --ioengine=libaio --name=test --filename=test --bs=4k --size=40G --readwrite=randrw --runtime=120 --time_based

test: (g=0): rw=randrw, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=libaio, iodepth=1

fio-3.1

Starting 1 process

Jobs: 1 (f=1): [f(1)][100.0%][r=39.5MiB/s,w=39.6MiB/s][r=10.1k,w=10.1k IOPS][eta 00m:00s]

test: (groupid=0, jobs=1): err= 0: pid=50892: Wed May 1 22:22:45 2019

read: IOPS=9805, BW=38.3MiB/s (40.2MB/s)(4596MiB/120001msec)

slat (usec): min=39, max=6678, avg=94.72, stdev=55.78

clat (nsec): min=450, max=18224, avg=525.83, stdev=120.10

lat (usec): min=39, max=6679, avg=95.36, stdev=55.79

clat percentiles (nsec):

| 1.00th=[ 462], 5.00th=[ 478], 10.00th=[ 482], 20.00th=[ 486],

| 30.00th=[ 490], 40.00th=[ 494], 50.00th=[ 502], 60.00th=[ 510],

| 70.00th=[ 516], 80.00th=[ 532], 90.00th=[ 596], 95.00th=[ 676],

| 99.00th=[ 860], 99.50th=[ 1048], 99.90th=[ 1384], 99.95th=[ 2480],

| 99.99th=[ 3728]

bw ( KiB/s): min= 720, max=40736, per=100.00%, avg=39389.00, stdev=5317.58, samples=239

iops : min= 180, max=10184, avg=9847.23, stdev=1329.39, samples=239

write: IOPS=9799, BW=38.3MiB/s (40.1MB/s)(4594MiB/120001msec)

slat (nsec): min=2982, max=106207, avg=4220.09, stdev=980.04

clat (nsec): min=407, max=18130, avg=451.48, stdev=103.71

lat (usec): min=3, max=111, avg= 4.74, stdev= 1.03

clat percentiles (nsec):

| 1.00th=[ 414], 5.00th=[ 418], 10.00th=[ 422], 20.00th=[ 430],

| 30.00th=[ 434], 40.00th=[ 434], 50.00th=[ 438], 60.00th=[ 438],

| 70.00th=[ 442], 80.00th=[ 446], 90.00th=[ 462], 95.00th=[ 588],

| 99.00th=[ 700], 99.50th=[ 916], 99.90th=[ 1208], 99.95th=[ 1288],

| 99.99th=[ 3536]

bw ( KiB/s): min= 752, max=42608, per=100.00%, avg=39366.63, stdev=5355.73, samples=239

iops : min= 188, max=10652, avg=9841.64, stdev=1338.93, samples=239

lat (nsec) : 500=69.98%, 750=28.64%, 1000=0.90%

lat (usec) : 2=0.42%, 4=0.04%, 10=0.01%, 20=0.01%

cpu : usr=2.20%, sys=10.85%, ctx=1176675, majf=0, minf=1372

IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%

submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%

complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%

issued rwt: total=1176625,1175958,0, short=0,0,0, dropped=0,0,0

latency : target=0, window=0, percentile=100.00%, depth=1

Run status group 0 (all jobs):

READ: bw=38.3MiB/s (40.2MB/s), 38.3MiB/s-38.3MiB/s (40.2MB/s-40.2MB/s), io=4596MiB (4819MB), run=120001-120001msec

WRITE: bw=38.3MiB/s (40.1MB/s), 38.3MiB/s-38.3MiB/s (40.1MB/s-40.1MB/s), io=4594MiB (4817MB), run=120001-120001msec

Disk stats (read/write):

nvme9n1: ios=1174695/883620, merge=0/0, ticks=105502/72225, in_queue=192101, util=99.28%

From vm:

[centos@kudu-1 nvme0]$ sudo fio --ioengine=libaio --name=test --filename=test --bs=4k --size=40G --readwrite=randrw --runtime=120 --time_based

test: (g=0): rw=randrw, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=libaio, iodepth=1

fio-3.1

Starting 1 process

Jobs: 1 (f=1): [m(1)][100.0%][r=29.2MiB/s,w=29.7MiB/s][r=7487,w=7595 IOPS][eta 00m:00s]

test: (groupid=0, jobs=1): err= 0: pid=44383: Wed May 1 12:22:24 2019

read: IOPS=6994, BW=27.3MiB/s (28.6MB/s)(3278MiB/120000msec)

slat (usec): min=54, max=20476, avg=115.27, stdev=71.45

clat (nsec): min=1757, max=31476, avg=2163.02, stdev=688.66

lat (usec): min=56, max=20481, avg=118.51, stdev=71.66

clat percentiles (nsec):

| 1.00th=[ 1800], 5.00th=[ 1832], 10.00th=[ 1864], 20.00th=[ 1992],

| 30.00th=[ 2040], 40.00th=[ 2064], 50.00th=[ 2064], 60.00th=[ 2096],

| 70.00th=[ 2096], 80.00th=[ 2128], 90.00th=[ 2480], 95.00th=[ 2544],

| 99.00th=[ 4448], 99.50th=[ 5536], 99.90th=[11072], 99.95th=[12736],

| 99.99th=[18560]

bw ( KiB/s): min= 952, max=31224, per=100.00%, avg=28153.51, stdev=4126.89, samples=237

iops : min= 238, max= 7806, avg=7038.23, stdev=1031.70, samples=237

write: IOPS=6985, BW=27.3MiB/s (28.6MB/s)(3274MiB/120000msec)

slat (usec): min=7, max=963, avg=12.60, stdev= 6.24

clat (nsec): min=1662, max=199250, avg=2030.26, stdev=712.33

lat (usec): min=10, max=970, avg=15.68, stdev= 6.48

clat percentiles (nsec):

| 1.00th=[ 1688], 5.00th=[ 1720], 10.00th=[ 1736], 20.00th=[ 1864],

| 30.00th=[ 1928], 40.00th=[ 1944], 50.00th=[ 1944], 60.00th=[ 1960],

| 70.00th=[ 1960], 80.00th=[ 1992], 90.00th=[ 2352], 95.00th=[ 2384],

| 99.00th=[ 4048], 99.50th=[ 4768], 99.90th=[11456], 99.95th=[13120],

| 99.99th=[19072]

bw ( KiB/s): min= 912, max=31880, per=100.00%, avg=28119.64, stdev=4176.38, samples=237

iops : min= 228, max= 7970, avg=7029.75, stdev=1044.07, samples=237

lat (usec) : 2=51.56%, 4=47.17%, 10=1.03%, 20=0.22%, 50=0.01%

lat (usec) : 250=0.01%

cpu : usr=4.96%, sys=28.37%, ctx=839307, majf=0, minf=26

IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%

submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%

complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%

issued rwt: total=839283,838268,0, short=0,0,0, dropped=0,0,0

latency : target=0, window=0, percentile=100.00%, depth=1

Run status group 0 (all jobs):

READ: bw=27.3MiB/s (28.6MB/s), 27.3MiB/s-27.3MiB/s (28.6MB/s-28.6MB/s), io=3278MiB (3438MB), run=120000-120000msec

WRITE: bw=27.3MiB/s (28.6MB/s), 27.3MiB/s-27.3MiB/s (28.6MB/s-28.6MB/s), io=3274MiB (3434MB), run=120000-120000msec

Disk stats (read/write):

nvme0n1: ios=838322/651596, merge=0/0, ticks=83804/22119, in_queue=104773, util=70.18%

Is there a way I can get near bare metal performance from my nvme block devices?

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