Is 1 vCPU on Google Compute Engine basically half of 1 physical CPU core?

multithreading google-cloud-platform google-compute-engine cpu-usage vcpu
gunit picture gunit · Aug 30, 2017 · Viewed 19.7k times · Source

Google's Machine types page states that:

For the n1 series of machine types, a virtual CPU is implemented as a single hardware hyper-thread on a 2.6 GHz Intel Xeon E5 (Sandy Bridge), 2.5 GHz Intel Xeon E5 v2 (Ivy Bridge)...etc

Assuming that a single physical CPU core with hyper-threading appears as two logical CPUs to an operating system, then if the n1-standard-2 machine that is described as 2 virtual CPUs and 7.5 GB of memory, then this essentially means 1 CPU core, right?

So if I'm trying to follow hardware recommendations for an InfluxDB instance that recommends 2 CPU cores, then I should aim for a Google Compute Engine machine that has 4vCPUs, correct?

Answer

pirhac picture pirhac · Aug 30, 2017

Typically when software tells you how many cores they need they don't take hyper-threading into account. Remember, AMD didn't even have that (Hyper-Threading) until very recently. So 2 cores means 2 vCPUs. Yes, a single HT CPU core shows up as 2 CPUs to the OS, but does NOT quite perform as 2 truly independent CPU cores.

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