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DescriptionSai Sindhur Malleni
2020-03-19 22:22:09 UTC
Description of problem:
Using a fully preallocated raw image and attaching it to a RHEL 8.1 guest with io=native and cache=none as follows,
virsh attach-disk rhel8 /var/lib/libvirt/images/raw-full.img vdb --cache none --io native --driver qemu --targetbus virtio --persistent
and then running, FIO with
ioengine=libaio
iodepth=32
direct=1
sync=0
depending on workload (random read/write, sequential read/write), there is a drop in performance when compared to RHEL 7.7 between 1 to 26%
Version-Release number of selected component (if applicable):
RHEL 8.1
Scenario RHEL 7.7 RHEL 8.1 % DIfference
write-4KiB 19210 17880 -6.92347735554399
write-64KiB 1511 1161 -23.1634679020516
write-1024KiB 99.19 72.53 -26.8777094465168
read-4KiB 21330 17480 -18.0496952648851
read-64KiB 1582 1161 -26.6118836915297
read-1024KiB 101 75.55 -25.1980198019802
randwrite-4KiB 307.3 287.4 -6.47575658965182
randwrite-64KiB 254 231.4 -8.89763779527559
randwrite-1024KiB 64.34 49.95 -22.365557973267
randread-4KiB 362.8 358 -1.32304299889747
randread-64KiB 287.7 269 -6.4998262078554
randread-1024KiB 61.03 51.25 -16.0249057840406
randrw-4KiB 333 306 -8.10810810810811
randrw-64KiB 273.7 243.5 -11.0339788089149
randrw-1024KiB 61.23 50.81 -17.0178017311775
How reproducible:
100%
Steps to Reproduce:
1. Launch a RHEL 8.1 guest on a RHEL 7.7 hypervisor and RHEL 8.1 hypervisor
2. Run FIO in the guest
3. Compare results
Actual results:
RHEL 8.1 performance lower than RHEL 7.7
Expected results:
RHEL 8.1 should perform equal to or better than RHEL 7.7
Additional info:
RHEL 8.1 guest is used in both cases for comparison
Comment 2Sai Sindhur Malleni
2020-03-19 22:31:08 UTC
The numbers in the bug description are IOPS. The CPU architecture is Haswell and the hypervisor has 56 logical cores. The disk is a spinning disk.
This BZ has been pending triage for 5-days and is being assigned to the qemu component contact for initial triage. Please review and determine if the BZ is assigned to the correct component (if not, please reassign), then review for proper ITR and Priority. Finally, add the Triaged keyword and reassign the BZ back to virt-maint to place it in the backlog.
Today I installed RHEL7 (and I also have RHEL8 installed already) on my home developement machine/server.
This should allow me to do more or less apples to apples benchmarks to compare and see if I can reproduce this, althought
it still be slow since I need to reboot the system in between OS changes.
I have bunch of relatively good NVME drives here as well to help with benchmarking.
Also as Stefan mentioned I do need as much as possible info about the enviroment used, including the RPM versions of the benchmarks.
Were the benchmarks running on same machine as well?
Moving to backlog for now although a decision may be made to just close as there's been no specific actions on this for quite a bit. Perhaps if tests were rerun using more recent versions of RHEL and RHEL-AV (e.g. 8.4.0 at least), then someone else could be assigned to look again.
Bulk update: Move RHEL8 bugs to RHEL9. If necessary to resolve in RHEL8, then clone to the current RHEL8 release.
Comment 15RHEL Program Management
2021-09-19 07:26:59 UTC
After evaluating this issue, there are no plans to address it further or fix it in an upcoming release. Therefore, it is being closed. If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.