Hi @sil2100, apologies for not providing an intuitive Impact field. I have updated it and hope it will be more helpful. Please let me know if you need more info.
** Description changed: [Impact] - See bug description + This bug affects users of Openstack Nova who want to create instances + that will leverage the realtime functionality that libvirt/qemu offers + by, amongst other things, pinning guest vcpus and qemu emulator threads + to specific pcpus. Nova provides the means for the user to control, via + the flavor hw:cpu_realtime_mask or image property hw_cpu_realtime_mask, + which physical cpus these resources will pinned to. This mask allows you + to mask the set of N pins that Nova selects such that 1 or more of your + vcpus can be declared "real-time" by ensuring that they do not have + emulator threads also pinned to them. The remaining "non-realtime" vcpus + will have vcpu and emulator threads colocated. The bug fixes the case + where e.g. you have a guest that has 2 vcpus (logically 0 and 1) and + Nova selects pcpus 14 and 22 and you have mask ^0 to indicate that you + want all but the first vcpu to be realtime. This should result in the + following being present in your libvirt xml for the guest: + + <cputune> + <vcpupin vcpu='0' cpuset='14'/> + <vcpupin vcpu='1' cpuset='22'/> + <emulatorpin cpuset='14'/> + <vcpusched vcpus='1' scheduler='fifo' priority='1'/> + </cputune> + + But (current only Mitaka since it does not have this patch) you will get + this: + + <cputune> + <vcpupin vcpu='0' cpuset='14'/> + <vcpupin vcpu='1' cpuset='22'/> + <emulatorpin cpuset='0'/> + <vcpusched vcpus='1' scheduler='fifo' priority='1'/> + </cputune> + + i.e. Nova will always set the emulator pin to be id of the vcpu instead + of the corresponding pcpu that it is pinned to. [Test Case] - * deploy openstack mitaka and configure nova.conf with vcpu-pin- + * deploy openstack mitaka and configure nova.conf with vcpu-pin- set=0,1,2,3 - https://pastebin.ubuntu.com/25133260/ + https://pastebin.ubuntu.com/25133260/ - * configure compute host kernel opts with "isolcpus=0,1,2,3" + reboot + * configure compute host kernel opts with "isolcpus=0,1,2,3" + reboot - * create flavor with: + * create flavor with: - openstack flavor create --public --ram 2048 --disk 10 --vcpus 2 --swap 0 test_flavor - openstack flavor set --property hw:cpu_realtime_mask='^0' test_flavor - openstack flavor set --property hw:cpu_policy=dedicated test_flavor - openstack flavor set --property hw:cpu_thread_policy=prefer test_flavor - openstack flavor set --property hw:cpu_realtime=yes test_flavor + openstack flavor create --public --ram 2048 --disk 10 --vcpus 2 --swap 0 test_flavor + openstack flavor set --property hw:cpu_realtime_mask='^0' test_flavor + openstack flavor set --property hw:cpu_policy=dedicated test_flavor + openstack flavor set --property hw:cpu_thread_policy=prefer test_flavor + openstack flavor set --property hw:cpu_realtime=yes test_flavor - * boot instance with ^^ flavor + * boot instance with ^^ flavor - * check that libvirt xml for vm has correct emulator pin cpuset # + * check that libvirt xml for vm has correct emulator pin cpuset # [Regression Potential] None expected. - ==== Description of problem: When using the cpu_realtime and cpu_realtim_mask flag to create new instance, the 'cpuset' of 'emulatorpin' option is using the id of vcpu which is incorrect. The id of host cpu should be used here. e.g. <cputune> <vcpupin vcpu='0' cpuset='2'/> <vcpupin vcpu='1' cpuset='3'/> <emulatorpin cpuset='0'/> ### the cpuset should be '2' here, when cpu_realtime_mask=^0. <vcpusched vcpus='1' scheduler='fifo' priority='1'/> </cputune> How reproducible: Boot new instance with cpu_realtime_mask flavor. Steps to Reproduce: 1. Create RT flavor nova flavor-create m1.small.performance 6 2048 20 2 nova flavor-key m1.small.performance set hw:cpu_realtime=yes nova flavor-key m1.small.performance set hw:cpu_realtime_mask=^0 nova flavor-key m1.small.performance set hw:cpu_policy=dedicated 2. Boot a instance with this flavor 3. Check the xml of the new instance Actual results: <cputune> <vcpupin vcpu='0' cpuset='2'/> <vcpupin vcpu='1' cpuset='3'/> <emulatorpin cpuset='0'/> <vcpusched vcpus='1' scheduler='fifo' priority='1'/> </cputune> Expected results: <cputune> <vcpupin vcpu='0' cpuset='2'/> <vcpupin vcpu='1' cpuset='3'/> <emulatorpin cpuset='2'/> <vcpusched vcpus='1' scheduler='fifo' priority='1'/> </cputune> ** Description changed: [Impact] This bug affects users of Openstack Nova who want to create instances that will leverage the realtime functionality that libvirt/qemu offers by, amongst other things, pinning guest vcpus and qemu emulator threads to specific pcpus. Nova provides the means for the user to control, via the flavor hw:cpu_realtime_mask or image property hw_cpu_realtime_mask, which physical cpus these resources will pinned to. This mask allows you to mask the set of N pins that Nova selects such that 1 or more of your vcpus can be declared "real-time" by ensuring that they do not have emulator threads also pinned to them. The remaining "non-realtime" vcpus will have vcpu and emulator threads colocated. The bug fixes the case where e.g. you have a guest that has 2 vcpus (logically 0 and 1) and Nova selects pcpus 14 and 22 and you have mask ^0 to indicate that you want all but the first vcpu to be realtime. This should result in the following being present in your libvirt xml for the guest: - <cputune> - <vcpupin vcpu='0' cpuset='14'/> - <vcpupin vcpu='1' cpuset='22'/> - <emulatorpin cpuset='14'/> - <vcpusched vcpus='1' scheduler='fifo' priority='1'/> - </cputune> + <cputune> + <vcpupin vcpu='0' cpuset='14'/> + <vcpupin vcpu='1' cpuset='22'/> + <emulatorpin cpuset='14'/> + <vcpusched vcpus='1' scheduler='fifo' priority='1'/> + </cputune> But (current only Mitaka since it does not have this patch) you will get this: - <cputune> - <vcpupin vcpu='0' cpuset='14'/> - <vcpupin vcpu='1' cpuset='22'/> - <emulatorpin cpuset='0'/> - <vcpusched vcpus='1' scheduler='fifo' priority='1'/> - </cputune> + <cputune> + <vcpupin vcpu='0' cpuset='14'/> + <vcpupin vcpu='1' cpuset='22'/> + <emulatorpin cpuset='0'/> + <vcpusched vcpus='1' scheduler='fifo' priority='1'/> + </cputune> i.e. Nova will always set the emulator pin to be id of the vcpu instead of the corresponding pcpu that it is pinned to. + + In terms of actual impact this could result in vcpus that are supposed + to be isolated not being so and therefore not behaving as expected. [Test Case] * deploy openstack mitaka and configure nova.conf with vcpu-pin- set=0,1,2,3 https://pastebin.ubuntu.com/25133260/ * configure compute host kernel opts with "isolcpus=0,1,2,3" + reboot * create flavor with: openstack flavor create --public --ram 2048 --disk 10 --vcpus 2 --swap 0 test_flavor openstack flavor set --property hw:cpu_realtime_mask='^0' test_flavor openstack flavor set --property hw:cpu_policy=dedicated test_flavor openstack flavor set --property hw:cpu_thread_policy=prefer test_flavor openstack flavor set --property hw:cpu_realtime=yes test_flavor * boot instance with ^^ flavor * check that libvirt xml for vm has correct emulator pin cpuset # [Regression Potential] None expected. ==== Description of problem: When using the cpu_realtime and cpu_realtim_mask flag to create new instance, the 'cpuset' of 'emulatorpin' option is using the id of vcpu which is incorrect. The id of host cpu should be used here. e.g. <cputune> <vcpupin vcpu='0' cpuset='2'/> <vcpupin vcpu='1' cpuset='3'/> <emulatorpin cpuset='0'/> ### the cpuset should be '2' here, when cpu_realtime_mask=^0. <vcpusched vcpus='1' scheduler='fifo' priority='1'/> </cputune> How reproducible: Boot new instance with cpu_realtime_mask flavor. Steps to Reproduce: 1. Create RT flavor nova flavor-create m1.small.performance 6 2048 20 2 nova flavor-key m1.small.performance set hw:cpu_realtime=yes nova flavor-key m1.small.performance set hw:cpu_realtime_mask=^0 nova flavor-key m1.small.performance set hw:cpu_policy=dedicated 2. Boot a instance with this flavor 3. Check the xml of the new instance Actual results: <cputune> <vcpupin vcpu='0' cpuset='2'/> <vcpupin vcpu='1' cpuset='3'/> <emulatorpin cpuset='0'/> <vcpusched vcpus='1' scheduler='fifo' priority='1'/> </cputune> Expected results: <cputune> <vcpupin vcpu='0' cpuset='2'/> <vcpupin vcpu='1' cpuset='3'/> <emulatorpin cpuset='2'/> <vcpusched vcpus='1' scheduler='fifo' priority='1'/> </cputune> -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1614054 Title: [SRU] Incorrect host cpu is given to emulator threads when cpu_realtime_mask flag is set To manage notifications about this bug go to: https://bugs.launchpad.net/cloud-archive/+bug/1614054/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
