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| -rw-r--r-- | README.md | 53 |
1 files changed, 52 insertions, 1 deletions
@@ -24,4 +24,55 @@ thinks that any time stolen from a task by the hypervisor belongs to the running task, thus this is only here to contrast the tested value we compute. -usage: `./vcpu_steal [seconds] [cpu]` +## building + +```bash +make + +./vcpu_steal +``` + +requirements: any c compiler, make + +## supported platforms + +this utility only works on linux! +we use `sched_setaffinity` and `cpu_set_t` for cpu pinning, both +linux-specific, hence the linux requirement. + +both `x86_64` (uses `rdtscp`) and `aarch64` (uses `cntvct_el0`) are supported. + +## usage + +```bash +./vcpu_steal [seconds] [cpu] +``` + +we run for **10 seconds**, on **cpu 0** by default if arguments not given. + +## output + +a 5-second run on vcpu 0 of a severely oversold vps: + +``` +ran at 2.795 GHz, for 117653562 iterations! + +kernel says: 3.108% stolen (wall=5000.04ms, cpu=4844.63ms, diff=155.41ms) +we say: 24.093% stolen (gaps=11607, total=1204.67ms, max=78.164ms) + +histogram: + <10us = 2369 + 10-50us = 7572 + 50-100us = 570 + 100-500us = 891 + 500us-1ms = 95 + 1-5ms = 73 + 5-10ms = 19 + >=10ms = 18 +``` + +the kernel reports only **3% stolen** due to it not having access to the +paravirtualized steal-time model-specific register. + +our detected value reports **24% stolen**, with one gap managing to last +for a whole 78ms! pretty bad! |