85 lines
2.7 KiB
Bash
Executable file
85 lines
2.7 KiB
Bash
Executable file
#!/bin/bash
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#
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# script to create cpusets to isolate CPU threads for KVM/libvirt VMs
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# requires 'cset'
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# available on Fedora through my COPR:
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# - https://copr.fedorainfracloud.org/coprs/jlay/cpuset/
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# review comments below regarding CPUs and XML entries
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#
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# this script:
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# - isolates host tasks from the VM CPUs
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# - applies some generic tweaks
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# - resets host isolation on VM shutdown
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#
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# define the CPUs (cores/threads) to isolate for the VM
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VM_CORES='0-20,24-44'
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# Tip: refer to 'virsh capabilities | grep siblings'
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# this will show CPU topology information for the host
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# allows one to pick optimal layout for the VM
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#
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# the pinned CPUs are definend like so in the VM libvirt XML:
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# <vcpupin vcpu='0' cpuset='0'/>
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# <vcpupin vcpu='1' cpuset='24'/>
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# <vcpupin vcpu='2' cpuset='1'/>
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# <vcpupin vcpu='3' cpuset='25'/>
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# [...]
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# <emulatorpin cpuset='10-11'/>
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#
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# NOTE: the pinned emulator CPUs must be included in VM_CORES
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# probably any iothreads too
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#
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# example above is based on a threadripper 3960x:
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# - one NUMA node
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# - SMT enabled
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#
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# reduce kernel jitter
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sudo sh -c 'sysctl vm.stat_interval=120 ; sysctl kernel.watchdog=0'
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# attempt to reset shielding, we want to create it with current params
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# and remove any existing slices from previous VM boots
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# we want it to be created with current params, such as possibly-changed pinned CPUs
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sudo cset shield --reset --sysset=host.slice --userset=windows10.slice || echo "something happened resetting shielding"
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# destroy old cpusets
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sudo cset set -d windows10.slice || echo "ignoring failure to destroy VM cpuset"
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sudo cset set -d host.slice || echo "ignoring failure to destroy host cpuset"
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# shield cores
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# userset slice must match the partition defined in libvirt xml, eg:
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#
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# </cputune>
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# <resource>
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# <partition>/windows10</partition>
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# </resource>
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# <os>
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sudo cset shield -c $VM_CORES --sysset=host.slice --userset=windows10.slice
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# start the VM
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virsh start windows10
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# determine QEMU vCPU PIDs
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QEMU_PIDS=$(sudo egrep 'vcpu.*pid' /var/run/libvirt/qemu/windows10.xml | cut -d\' -f4)
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# set higher priority for vCPU PIDs
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sudo renice -20 -p ${QEMU_PIDS}
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# either of these attempts at real time seem to freeze on boot
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# try a different kernel (not 5.8.11)
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#for CPUPID in ${QEMU_PIDS}; do
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## sudo chrt -f -p 99 ${CPUPID}
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# sudo chrt -r -p 99 ${CPUPID}
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#done
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echo "Waiting for windows10 VM to stop before resetting cpusets"
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while true; do
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# chill a bit
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sleep 10
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# get vm state, check if it's off
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if test -f "/var/run/libvirt/qemu/windows10.xml"; then
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VM_STATE="on" # doesn't do much (yet?), just here to fill a spot
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else
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VM_STATE="off"
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echo -e "windows10 VM shut down, setting cpusets back to normal\n"
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sudo cset shield --reset --sysset=host.slice --userset=windows10.slice
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exit 0
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fi
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done
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