Bug 820081
Summary: | smp affinity behavior differs between 6.3 guest and 6.3 host after cpu offline/online | ||
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Product: | Red Hat Enterprise Linux 6 | Reporter: | Shaolong Hu <shu> |
Component: | qemu-kvm | Assignee: | Igor Mammedov <imammedo> |
Status: | CLOSED WORKSFORME | QA Contact: | Virtualization Bugs <virt-bugs> |
Severity: | medium | Docs Contact: | |
Priority: | medium | ||
Version: | 6.3 | CC: | acathrow, areis, bsarathy, chayang, juzhang, knoel, michen, mkenneth, qzhang, shuang, shu, virt-bugs, virt-maint |
Target Milestone: | rc | ||
Target Release: | --- | ||
Hardware: | Unspecified | ||
OS: | Unspecified | ||
Whiteboard: | |||
Fixed In Version: | Doc Type: | Bug Fix | |
Doc Text: | Story Points: | --- | |
Clone Of: | Environment: | ||
Last Closed: | 2014-08-29 15:41:33 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: | 833569 |
Description
Shaolong Hu
2012-05-09 05:55:13 UTC
host has 4 processors: [root@localhost ~]# cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 23 model name : Intel(R) Core(TM)2 Quad CPU Q9500 @ 2.83GHz guest cmd: /usr/libexec/qemu-kvm -enable-kvm -M rhel6.3.0 -m 4G -name rhel6.3-64 -rtc base=utc,clock=host,driftfix=slew -no-kvm-pit-reinjection -uuid 3f2ea5cd-3d29-48ff-aab2-23df1b6ae213 -drive file=nfs/RHEL-Server-6.3-64-virtio.qcow2,cache=none,if=none,rerror=stop,werror=stop,id=drive-virtio-disk0,format=qcow2 -device virtio-blk-pci,drive=drive-virtio-disk0,id=device-virtio-disk0 -netdev tap,id=netdev0,fd=6 6<>/dev/tap6 -device virtio-net-pci,netdev=netdev0,id=device-net0,mac=02:a3:a6:ed:4b:94 -boot order=cd -monitor stdio -usb -device usb-tablet,id=input0 -chardev socket,id=s1,path=/tmp/s1,server,nowait -device isa-serial,chardev=s1 -vnc :10 -monitor tcp::1234,server,nowait -qmp tcp:0:5555,server,nowait -chardev socket,id=qmp_monitor_id_qmpmonitor1,path=/tmp/qmp,server,nowait -mon chardev=qmp_monitor_id_qmpmonitor1,mode=control -smp 4 This request was not resolved in time for the current release. Red Hat invites you to ask your support representative to propose this request, if still desired, for consideration in the next release of Red Hat Enterprise Linux. This request was erroneously removed from consideration in Red Hat Enterprise Linux 6.4, which is currently under development. This request will be evaluated for inclusion in Red Hat Enterprise Linux 6.4. There were several related patches on rhkml, it might be fixed by now. Please retest. pls move to 6.6 due to limited capacity and still being tech-preview Hi Shu, Can you reply comment10? Best Regards, Junyi I've tested with 2.6.32-498.el6.x86_64 kernel on AMD/Intel hosts and VM using ahci IRQ. As result behaviour between physical hosts and VM was the same. (Make sure that irqbalance service is turned off so that it won't screw up results) test env: 4 core host/VM with nox2apic option on kernel command line to make sure that APIC would be in flat mode and do RR IRQ balancing. 1. set smp_affinity for ahci IRQ to 'f' 2. create load: dd =if=/dev/sda of=/dev/null * watch ahci IRQ load RR distributed among 4 CPUs 3. offline CPU1 4. online CPU1 * ahci IRQ is not distributed to CPU1 (phys hosts and VM) 5. re-et smp_affinity for ahci IRQ to 'f' * that retriggers IRQ distribution and it's handled on all 4 CPUs again Conclusion: * kernel doesn't distribe IRQ to hotplugged CPU when doing RR in flat mode, it never worked ()regardles if it's VM or baremetal) and need to be fixed ustream if someone asks for it. * to force IRQ routing change after CPU hotplug re-set smp-affinity for IRQ * closing bug as worksforme (baremetal and VM behave identically) The needinfo request[s] on this closed bug have been removed as they have been unresolved for 1000 days |