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Aleksei Sviridkin
b1b8cbecc2
Every CPU reading on this failure path has a subject inside the sandbox: a cgroup, a tenant worker's threads, a sandbox node's own /proc/stat. Each of them can say a guest was given its ticks while getting no work done, and none can say what the layers above spent. That is where this suite's own tax is paid: the sandbox nodes' guest time is charged to the runner kernel as user time, and whatever the runner VM loses to the machine hosting it is charged to nobody the sandbox can see. Two readings close that. /proc/stat is not namespaced, so reading it from the sandbox container reads the runner VM's kernel -- the only place steal on that layer appears, which is what separates a slow suite from a machine sharing a core with somebody else. The sandbox VMs are QEMU processes in this container's own PID namespace, so their threads are a local read too, and they say which node spent the kernel's user time and whether the three spent it evenly. Both are taken at the same two points as the KVM counters and for the same reason: the values are cumulative, so a rate needs a pair, and the interval worth measuring is the window the guest is failing to boot in. The thread reading runs the probe the worker capture already uses rather than a copy of it, since a second copy would drift exactly at the failure paths. Each carries the layer it describes in its own legend, because three kernels in this report publish a /proc/stat and two captures read QEMU threads, one layer apart in each direction -- and a reader who takes one for the other compares a hypervisor against its own guest. Assisted-By: Claude <noreply@anthropic.com> Signed-off-by: Aleksei Sviridkin <3811295@gmail.com>