Bug 2012226

Summary: High cpu usage of cppc_fie even when idle
Product: [Fedora] Fedora Reporter: russ.butler
Component: kernelAssignee: Jeremy Linton (ARM) <jlinton>
Status: CLOSED CURRENTRELEASE QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 35CC: acaringi, adscvr, airlied, alciregi, bskeggs, hdegoede, jarodwilson, jeremy, jeremy.linton, jglisse, jonathan, josef, kernel-maint, lgoncalv, linville, masami256, mchehab, ptalbert, pwhalen, russ.butler, steved
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Hardware: aarch64   
OS: Linux   
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Last Closed: 2022-10-19 18:21:23 UTC Type: Bug
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Bug Blocks: 245418    

Description russ.butler 2021-10-08 15:24:20 UTC 
Description of problem:
High cpu usage of cppc_fie (1.5-2.5%) when idle

Version-Release number of selected component (if applicable):
Fedora Linux 35 (Server Edition Prerelease)


How reproducible:
CPU usage is constantly hovers between 1.5 and 2.5% - very reproducible.


Steps to Reproduce:
1. Install Fedora 35 server edition on an aarch64 Ampere Altra machine.
2. Use top to view that CPU usage


Actual results:
CPU usage is between 1.5% and 2.5% when the machine is idle


Expected results:
CPU usage is less than 0.75 1.5% and 2.5% when the machine is idle
Comment 1 Jeremy Linton 2021-10-14 20:04:56 UTC 
Then this isn't specific to my hacked up rpi4 with unmerged TFA/uefi patches to enable CPPC. This might be pretty significant if it is not an accounting problem. I saw this in 5.14 and instrumented the cppc call path to see if it was making excessive mailbox inquiries and it didn't appear to be the case.
Comment 2 Jeremy Linton 2022-07-26 15:09:47 UTC 
Fix posted: https://lkml.org/lkml/2022/7/26/679

(although thinking about it I probably should have hidden the module parm or at least flipped its value if FIE is disabled)
Comment 3 Jeremy Linton 2022-10-19 18:21:23 UTC 
This is fixed closing.