I have identified the cause of the fio/glusterfs crash and the EXT4-fs errors: The test procedure runs fio write tests on /dev/sda (which is in fact the rootfs itself). I modified Phil's launch script to create a smaller 10GB boot disk for the rootfs but also create a 50GB "junk" disk (/dev/sdb) to use for the fio test:
https://paste.ubuntu.com/p/9Gp7rqR2yG/ (modified launch script) Then, run the fio test like so: # NOTE: /dev/sdb instead of /dev/sda 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/sdb This yields a clean test run (no crash, no EXT4 corruption errors) with either kernel version, however I still see the same performance degradation with 5.15-generic vs 5.4-kvm running on the focal cloudimg. For the record, I also tested updating glusterfs and libaio to the most modern versions, with no effect (but again, the "glusterfs crash" was a red herring). -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. 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 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2042564/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
