Bug 1796356
| Summary: | ksmd using heavy CPU on AMD sev | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux Advanced Virtualization | Reporter: | Dr. David Alan Gilbert <dgilbert> |
| Component: | qemu-kvm | Assignee: | Dr. David Alan Gilbert <dgilbert> |
| qemu-kvm sub component: | General | QA Contact: | zixchen |
| Status: | CLOSED ERRATA | Docs Contact: | |
| Severity: | unspecified | ||
| Priority: | unspecified | CC: | aarcange, brijesh.singh, chayang, coli, ehadley, jinzhao, juzhang, mrezanin, virt-maint, yuhuang, zixchen |
| Version: | 8.1 | ||
| Target Milestone: | rc | ||
| Target Release: | 8.0 | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Whiteboard: | |||
| Fixed In Version: | qemu-kvm-5.0.0-0.module+el8.3.0+6620+5d5e1420 | Doc Type: | If docs needed, set a value |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2020-11-17 17:46:36 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | |||
| Bug Blocks: | 1818024 | ||
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Description
Dr. David Alan Gilbert
2020-01-30 09:22:02 UTC
Posted upstream fix: [PATCH] machine/memory encryption: Disable mem merge QEMU has been recently split into sub-components and as a one-time operation to avoid breakage of tools, we are setting the QEMU sub-component of this BZ to "General". Please review and change the sub-component if necessary the next time you review this BZ. Thanks This is now merged upstream as 4ba59be1d6d8c57941841a505cb4656628d582d0 Given that disabling ksm manually is an OK work around, I don't intend to backport it unless someone requests it. Moving to post and marking fixed in 5.0 Reproduce bug with qemu-kvm-4.2.0-29.module+el8.2.1+7297+a825794d.x86_64. As the tested machine has 64GB memory, I installed vm with 50G RAM. After 40 mins, it takes 13% CPU usage:
Version:
kernel-4.18.0-193.13.2.el8_2.x86_64
qemu-kvm-4.2.0-29.module+el8.2.1+7297+a825794d.x86_64
Steps:
1. start a vm with 50GB RAM, and leave it idle.
2. systemctl start/enable ksm
3. systemctl status ksm checked its status is enabled.
4. start top on host
5. wait for 40 mins
Results:
After Step 4, ksmd usage is around 1.6% CPU usage, rising up to approximately 13%.
Verified bug with qemu-kvm-5.0.0-0.module+el8.3.0+6620+5d5e1420.x86_64, using top command didn't capture ksmd cpu usage.
Version:
kernel-4.18.0-224.el8.x86_64
qemu-kvm-5.0.0-2.module+el8.3.0+7379+0505d6ca.x86_64
Steps:
1. start a vm with 50GB RAM, and leave it idle.
2. systemctl start/enable ksm
3. systemctl status ksm checked its status is enabled.
4. start top on host
5. wait for 40 mins
Actual Result:
After Step 4 and Step 5, ksm service status is active,start top command can't see ksmd cpu usage both from the beginning and after 40 mins.
● ksm.service - Kernel Samepage Merging
Loaded: loaded (/usr/lib/systemd/system/ksm.service; enabled; vendor preset: enabled)
Active: active (exited) since Tue 2020-07-21 08:22:25 EDT; 1min 18s ago
Main PID: 36612 (code=exited, status=0/SUCCESS)
Tasks: 0 (limit: 407449)
Memory: 0B
CGroup: /system.slice/ksm.service
Jul 21 08:22:25 dell-per7425-02.khw.lab.eng.bos.redhat.com systemd[1]: Starting Kernel Samepage Merging...
Jul 21 08:22:25 dell-per7425-02.khw.lab.eng.bos.redhat.com systemd[1]: Started Kernel Samepage Merging.
***************************************************************************************************************
From the beginning:
Tasks: 989 total, 2 running, 987 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
MiB Mem : 63865.6 total, 7913.6 free, 53241.7 used, 2710.3 buff/cache
MiB Swap: 32096.0 total, 32096.0 free, 0.0 used. 9981.1 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
34197 qemu 20 0 55.0g 50.1g 22052 S 1.3 80.3 1:56.46 qemu-kvm
36989 root 20 0 62684 5660 3784 R 1.0 0.0 0:01.74 top
34252 root 20 0 0 0 0 S 0.3 0.0 0:01.03 kvm-pit/34197
1 root 20 0 247864 14756 9412 S 0.0 0.0 0:06.99 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.06 kthreadd
****************************************************************************************************************
After 60 mins:
Tasks: 995 total, 1 running, 994 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
MiB Mem : 63865.6 total, 7879.5 free, 53266.7 used, 2719.4 buff/cache
MiB Swap: 32096.0 total, 32096.0 free, 0.0 used. 9954.3 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
34197 qemu 20 0 55.0g 50.1g 22052 S 2.3 80.3 2:44.95 qemu-kvm
38106 root 20 0 62684 5680 3796 R 0.7 0.0 0:14.98 top
2304 root 20 0 125380 6028 4908 S 0.3 0.0 0:04.59 irqbalance
1 root 20 0 247864 14756 9412 S 0.0 0.0 0:07.01 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.07 kthreadd
Expected results:
Sane ksm usage
Needinfo: could you please check the test steps and the actual result is as expected, as ksmd is not monitored in the cpu usage, thank you.
(In reply to zixchen from comment #8) > Needinfo: could you please check the test steps and the actual result is as > expected, as ksmd is not monitored in the cpu usage, thank you. The test needs to be running the VM with SEV enabled - are you doing that? (In reply to Dr. David Alan Gilbert from comment #9) The test needs to be running the VM with SEV enabled - are you doing that? yes, sev is enabled in the VM. Steps: 1. ssh login to the VM. 2. dmesg | grep sev After Step2, [ 0.001000] AMD Secure Encrypted Virtualization (SEV) active OK, then great, that test is fine. Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory (virt:8.3 bug fix and enhancement update), and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2020:5137 |