Bug 470204

Summary: add s390 and s390x into ExclusiveArch
Product: [Fedora] Fedora Reporter: Dan Horák <dan>
Component: irqbalanceAssignee: Neil Horman <nhorman>
Status: CLOSED NOTABUG QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: medium Docs Contact:
Priority: medium    
Version: 9CC: dennis, gmuelas, nhorman
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Target Release: ---   
Hardware: s390x   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
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Clone Of: Environment:
Last Closed: 2008-11-06 14:35:42 EST Type: ---
Regression: --- Mount Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On:    
Bug Blocks: 467765    

Description Dan Horák 2008-11-06 04:19:51 EST 
Please add s390 and s390x into ExclusiveArch, because irqbalance does work/compile there.

Adding dgilmore to CC as he can require/decline similar action for Fedora on Sparc.
Comment 1 Neil Horman 2008-11-06 14:35:42 EST 
I believe that it compiles and even runs without error on s390 (given that its only interface to the kernel is via /proc).  That being said however, I can't find any reason why its usefull on those arches.  While one can steer interrupts to various cpus in a guest account (either via irqbalance, or manually via /proc/irq/<irq #>/smp_affinity), theres no guarantee that those interrupts will actually be steered to different physical cpus.  Since you're always running on a hypervisor on these arches, theres always going to be a disconnect between what irqblance tries to do and what acutally happens on the metal.  If you can come up with some evidence that irqbalance produces a benefit on these systems consistently and predictably, then I'll happily consider it, but just the fact that its runs without falling over isn't reason enough to enable it.
Comment 2 Gonzalo Muelas Serrano 2008-11-10 09:57:00 EST 
From what I understood from one of our s390[x] kernel developers, he agrees with Neil: the interrupts in s390 are floating interrupts, that is, is not possible/there is no intention to choose the CPU, so s390x won't benefit form irqbalance.