For reference, I also tried on a 22.04 cloud image with 5.15 kernel
```
ubuntu@cloudimg:~$ sudo fio --ioengine=libaio --blocksize=4k --readwrite=write
--filesize=40G --end_fsync=1 --iodepth=128 --direct=1 --group_reporting
--numjobs=8 --name=fiojob1 --filename=/dev/sda
fiojob1: (g=0): rw=write, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B,
ioengine=libaio, iodepth=128
...
fio-3.28
Starting 8 processes
Jobs: 1 (f=1): [_(5),W(1),_(2)][100.0%][w=311MiB/s][w=79.7k IOPS][eta 00m:00s]
fiojob1: (groupid=0, jobs=8): err= 0: pid=2198: Thu Nov 2 13:42:07 2023
write: IOPS=244k, BW=952MiB/s (998MB/s)(320GiB/344252msec); 0 zone resets
slat (nsec): min=655, max=86425k, avg=6303.33, stdev=121079.62
clat (usec): min=5, max=124812, avg=4182.79, stdev=3154.25
lat (usec): min=61, max=124814, avg=4189.52, stdev=3155.57
clat percentiles (usec):
| 1.00th=[ 553], 5.00th=[ 1319], 10.00th=[ 1713], 20.00th=[ 2180],
| 30.00th=[ 2638], 40.00th=[ 3064], 50.00th=[ 3523], 60.00th=[ 4015],
| 70.00th=[ 4621], 80.00th=[ 5538], 90.00th=[ 7177], 95.00th=[ 9110],
| 99.00th=[15270], 99.50th=[19792], 99.90th=[34866], 99.95th=[42206],
| 99.99th=[64226]
bw ( KiB/s): min=197710, max=1710611, per=100.00%, avg=978380.45,
stdev=38019.38, samples=5483
iops : min=49424, max=427652, avg=244594.42, stdev=9504.89,
samples=5483
lat (usec) : 10=0.01%, 20=0.01%, 50=0.01%, 100=0.01%, 250=0.01%
lat (usec) : 500=0.79%, 750=0.82%, 1000=0.95%
lat (msec) : 2=13.06%, 4=44.04%, 10=36.63%, 20=3.21%, 50=0.45%
lat (msec) : 100=0.03%, 250=0.01%
cpu : usr=3.34%, sys=7.56%, ctx=978696, majf=0, minf=122
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=100.0%
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=0.1%
issued rwts: total=0,83886080,0,0 short=0,0,0,0 dropped=0,0,0,0
latency : target=0, window=0, percentile=100.00%, depth=128
Run status group 0 (all jobs):
WRITE: bw=952MiB/s (998MB/s), 952MiB/s-952MiB/s (998MB/s-998MB/s), io=320GiB
(344GB), run=344252-344252msec
Disk stats (read/write):
sda: ios=336/33974149, merge=0/49890543, ticks=201/35842485,
in_queue=35842765, util=100.00%
ubuntu@cloudimg:~$ uname --kernel-release
5.15.0-87-generic
```
This shows bw=952MiB/s
Summary:
Ubuntu 22.04 5.15 kernel `bw=952MiB/s`
Ubuntu 20.04 5.4 kernel `bw=1237MiB/s`
Ubuntu 20.04 5.15 kernel `bw=605MiB/s`
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https://bugs.launchpad.net/bugs/2042564
Title:
Performance regression in the 5.15 Ubuntu 20.04 kernel compared to 5.4
Ubuntu 20.04 kernel
Status in linux package in Ubuntu:
New
Status in linux source package in Focal:
New
Bug description:
We in the Canonical Public Cloud team have received report from our
colleagues in Google regarding a potential performance regression with
the 5.15 kernel vs the 5.4 kernel on ubuntu 20.04. Their test were
performed using the linux-gkeop and linux-gkeop-5.15 kernels.
I have verified with the generic Ubuntu 20.04 5.4 linux-generic and
the Ubuntu 20.04 5.15 linux-generic-hwe-20.04 kernels.
The tests were run using `fio`
fio commands:
* 4k initwrite: `fio --ioengine=libaio --blocksize=4k --readwrite=write
--filesize=40G --end_fsync=1 --iodepth=128 --direct=1 --group_reporting
--numjobs=8 --name=fiojob1 --filename=/dev/sdc`
* 4k overwrite: `fio --ioengine=libaio --blocksize=4k --readwrite=write
--filesize=40G --end_fsync=1 --iodepth=128 --direct=1 --group_reporting
--numjobs=8 --name=fiojob1 --filename=/dev/sdc`
My reproducer was to launch an Ubuntu 20.04 cloud image locally with qemu the
results are below:
Using 5.4 kernel
```
ubuntu@cloudimg:~$ uname --kernel-release
5.4.0-164-generic
ubuntu@cloudimg:~$ sudo fio --ioengine=libaio --blocksize=4k
--readwrite=write --filesize=40G --end_fsync=1 --iodepth=128 --direct=1
--group_reporting --numjobs=8 --name=fiojob1 --filename=/dev/sda
fiojob1: (g=0): rw=write, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T)
4096B-4096B, ioengine=libaio, iodepth=128
...
fio-3.16
Starting 8 processes
Jobs: 8 (f=8): [W(8)][99.6%][w=925MiB/s][w=237k IOPS][eta 00m:01s]
fiojob1: (groupid=0, jobs=8): err= 0: pid=2443: Thu Nov 2 09:15:22 2023
write: IOPS=317k, BW=1237MiB/s (1297MB/s)(320GiB/264837msec); 0 zone resets
slat (nsec): min=628, max=37820k, avg=7207.71, stdev=101058.61
clat (nsec): min=457, max=56099k, avg=3222240.45, stdev=1707823.38
lat (usec): min=23, max=56100, avg=3229.78, stdev=1705.80
clat percentiles (usec):
| 1.00th=[ 775], 5.00th=[ 1352], 10.00th=[ 1647], 20.00th=[ 2024],
| 30.00th=[ 2343], 40.00th=[ 2638], 50.00th=[ 2933], 60.00th=[ 3261],
| 70.00th=[ 3654], 80.00th=[ 4146], 90.00th=[ 5014], 95.00th=[ 5932],
| 99.00th=[ 8979], 99.50th=[10945], 99.90th=[18220], 99.95th=[22676],
| 99.99th=[32113]
bw ( MiB/s): min= 524, max= 1665, per=100.00%, avg=1237.72, stdev=20.42,
samples=4232
iops : min=134308, max=426326, avg=316855.16, stdev=5227.36,
samples=4232
lat (nsec) : 500=0.01%, 750=0.01%, 1000=0.01%
lat (usec) : 4=0.01%, 10=0.01%, 20=0.01%, 50=0.01%, 100=0.01%
lat (usec) : 250=0.05%, 500=0.54%, 750=0.37%, 1000=0.93%
lat (msec) : 2=17.40%, 4=58.02%, 10=22.01%, 20=0.60%, 50=0.07%
lat (msec) : 100=0.01%
cpu : usr=3.29%, sys=7.45%, ctx=1262621, majf=0, minf=103
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=100.0%
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=0.1%
issued rwts: total=0,83886080,0,8 short=0,0,0,0 dropped=0,0,0,0
latency : target=0, window=0, percentile=100.00%, depth=128
Run status group 0 (all jobs):
WRITE: bw=1237MiB/s (1297MB/s), 1237MiB/s-1237MiB/s (1297MB/s-1297MB/s),
io=320GiB (344GB), run=264837-264837msec
Disk stats (read/write):
sda: ios=36/32868891, merge=0/50979424, ticks=5/27498602, in_queue=1183124,
util=100.00%
```
After upgrading to linux-generic-hwe-20.04 kernel and rebooting
```
ubuntu@cloudimg:~$ uname --kernel-release
5.15.0-88-generic
ubuntu@cloudimg:~$ sudo fio --ioengine=libaio --blocksize=4k
--readwrite=write --filesize=40G --end_fsync=1 --iodepth=128 --direct=1
--group_reporting --numjobs=8 --name=fiojob1 --filename=/dev/sda
fiojob1: (g=0): rw=write, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T)
4096B-4096B, ioengine=libaio, iodepth=128
...
fio-3.16
Starting 8 processes
Jobs: 1 (f=1): [_(7),W(1)][100.0%][w=410MiB/s][w=105k IOPS][eta 00m:00s]
fiojob1: (groupid=0, jobs=8): err= 0: pid=1438: Thu Nov 2 09:46:49 2023
write: IOPS=155k, BW=605MiB/s (634MB/s)(320GiB/541949msec); 0 zone resets
slat (nsec): min=660, max=325426k, avg=10351.04, stdev=232438.50
clat (nsec): min=1100, max=782743k, avg=6595008.67, stdev=6290570.04
lat (usec): min=86, max=782748, avg=6606.08, stdev=6294.03
clat percentiles (usec):
| 1.00th=[ 914], 5.00th=[ 2180], 10.00th=[ 2802], 20.00th=[ 3556],
| 30.00th=[ 4178], 40.00th=[ 4817], 50.00th=[ 5538], 60.00th=[ 6259],
| 70.00th=[ 7177], 80.00th=[ 8455], 90.00th=[ 10683], 95.00th=[ 13566],
| 99.00th=[ 26870], 99.50th=[ 34866], 99.90th=[ 63177], 99.95th=[ 80217],
| 99.99th=[145753]
bw ( KiB/s): min=39968, max=1683451, per=100.00%, avg=619292.10,
stdev=26377.19, samples=8656
iops : min= 9990, max=420862, avg=154822.58, stdev=6594.34,
samples=8656
lat (usec) : 2=0.01%, 4=0.01%, 10=0.01%, 20=0.01%, 50=0.01%
lat (usec) : 100=0.01%, 250=0.01%, 500=0.05%, 750=0.48%, 1000=0.65%
lat (msec) : 2=2.79%, 4=23.00%, 10=60.93%, 20=10.08%, 50=1.83%
lat (msec) : 100=0.16%, 250=0.02%, 500=0.01%, 1000=0.01%
cpu : usr=3.27%, sys=7.39%, ctx=1011754, majf=0, minf=93
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=100.0%
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=0.1%
issued rwts: total=0,83886080,0,8 short=0,0,0,0 dropped=0,0,0,0
latency : target=0, window=0, percentile=100.00%, depth=128
Run status group 0 (all jobs):
WRITE: bw=605MiB/s (634MB/s), 605MiB/s-605MiB/s (634MB/s-634MB/s),
io=320GiB (344GB), run=541949-541949msec
Disk stats (read/write):
sda: ios=264/31713991, merge=0/52167896, ticks=127/57278442,
in_queue=57278609, util=99.95%
```
I have shared the results with xnox and the important datapoints to
see are `bw=1237MiB/s` with the 5.4 kernel and only `bw=605MiB/s` with
the 5.15 kernel.
Attached find the test results initially reported by our google
colleagues
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