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--- eve-kvm:core-isolation [2026/09/18 18:05] – mc
+++ eve-kvm:core-isolation [2026/09/19 17:35] (current) – mc
@@ Line 6: / Line 6: @@
 **Time required.** About 20 minutes, including one reboot.
+**Just here to run the demo?** Use the four-act script immediately below. The numbered steps in Parts 1-4 are the full procedure behind it.
+----
+===== Quick demo script — 1, 2, 3, 4 =====
+Four commands-and-a-sentence. Run them in order, with the pinned VM **not yet deployed**.
+Set this up first so every command is a single keystroke away:
+<code bash>
+alias iso='echo "isolated: [$(cat /sys/devices/system/cpu/isolated)]"'
+alias pools='cat /run/domainmgr/CPUPoolStatus/*.json'
+alias plan='cat /run/domainmgr/cpuplan.json'
+alias ticks='awk "/^cpu[0-9] /{printf \"%s=%s  \", \$1, \$2+\$4}" /proc/stat; echo'
+</code>
+==== 1. BEFORE — a plain node: no isolation, no assignment ====
+<code bash>
+iso
+pools
+ticks
+</code>
+<code>
+isolated: []
+{"Pools":[{"Kind":1,"CPUs":[0,1,2,3,4,5,6,7],"FreeCPUs":[1,2,3,4,5,6,7],"TotalCores":4,"FreeWholeCores":3},
+          {"Kind":2,"CPUs":null},{"Kind":3,"CPUs":null}]}
+cpu0=73851  cpu1=586  cpu2=496  cpu3=390  cpu4=1120  cpu5=980  cpu6=842  cpu7=771
+</code>
+**Say:** "The kernel isolates nothing. There is one pool — all eight threads, shared. Every CPU is doing work. Any workload can be scheduled anywhere, and so can the kernel's own housekeeping."
+//This is the state before any configuration. If your node is already configured and you want to rehearse the whole arc, revert it with:// ''eve config mount /tmp/cfg && rm /tmp/cfg/grub.cfg && eve config unmount && reboot'' //— or just show a saved capture of this output.//
+==== 2. AFTER the config — the isolated pool exists, and nobody may use it ====
+Enable per Part 2 (property, ''grub.cfg'', reboot), then:
+<code bash>
+iso
+pools
+ticks
+</code>
+<code>
+isolated: [4-7]
+{"Pools":[{"Kind":1,"CPUs":[0,1,2,3,4,5,6,7],"FreeCPUs":[2,3],"AllocatedThreads":6,"FreeWholeCores":1},
+          {"Kind":2,"CPUs":null},
+          {"Kind":3,"CPUs":[4,5,6,7],"FreeCPUs":[4,5,6,7],"TotalCores":2,"FreeWholeCores":2}]}
+cpu0=9525  cpu1=376  cpu2=496  cpu3=390  cpu4=0  cpu5=0  cpu6=0  cpu7=0
+</code>
+**Say:** "Now there are three pools. Four CPUs are isolated. Look at the housekeeping pool — of eight threads, six are gone: two reserved for EVE, four withheld for isolation. Only one whole core is left for ordinary work. And cores 4 through 7 have executed **zero** cycles since boot — not the scheduler, not a workload, nothing."
+**Point at:** ''FreeWholeCores'' dropping 3 → 1, and the four zeros.
+==== 3. DEPLOY — a pinned VM takes an isolated core ====
+Deploy a **2-vCPU** app with CPU pinning enabled, then:
+<code bash>
+plan
+pools
+</code>
+<code>
+{ "display_name": "TF-STND-VM-1", "mode": "whole-core-smt", "vcpus": 2,
+  "status": "success", "host_cpus": [4, 5] }
+{"Pools":[{"Kind":1,"CPUs":[0,1,2,3,6,7],"FreeCPUs":[2,3],"FreeWholeCores":1},
+          {"Kind":2,"CPUs":[4,5],"AllocatedThreads":2},
+          {"Kind":3,"CPUs":[4,5,6,7],"FreeCPUs":[6,7],"FreeWholeCores":1}]}
+</code>
+**Say:** "Two vCPUs, one whole physical core, taken from the isolated set — cores 4 and 5. The isolated pool drops from two free cores to one. The app asked for nothing but 'CPU pinning'; the node-level switch did the rest."
+==== 4. PROVE IT — the kernel agrees, down to the thread ====
+<code bash>
+PID=$(pgrep -f qemu-system | head -1)
+for t in /proc/$PID/task/*; do
+  printf '%-18s %s
+' "$(cat $t/comm)" "$(awk '/Cpus_allowed_list/{print $2}' $t/status)"
+done | sort -u
+cat /sys/fs/cgroup/cpuset/eve-user-apps/*.1/cpuset.cpus
+ticks
+</code>
+<code>
+qemu-system-x86    4         <-- vCPU 0
+qemu-system-x86    5         <-- vCPU 1
+qemu-system-x86    4-5       <-- emulator / IO threads
+vhost-7981         4-5
+-5
+cpu0=9525  cpu1=376  cpu2=496  cpu3=390  cpu4=1990  cpu5=813  cpu6=0  cpu7=0
+</code>
+**Say:** "One vCPU thread per hardware thread, pinned 1:1. Everything else the VM needs is confined to the same core. The cgroup agrees. And the second isolated core is **still at zero** — it is reserved and untouchable, waiting for the next workload that asks."
+**The closing line:** cores 6 and 7 are idle and cannot be used by anything that did not ask for isolation. On this node, a workload that needs guaranteed CPU gets it — not by priority, not by best effort, but because nothing else is allowed to run there.
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