I'm using python locust for performance testing. I mostly use java and in java 1 cpu thread = java thread. So if i have VM with 12 threads, I can perform only 12 actions in parallel.

But locust has parameter USERS which stands for "Peak number of concurrent Locust users". Does it work the same way? If i put USERS = 25 but VM has only 12 threads, will it mean that simultaneously it will execute only 12 actions in parallel and the rest will wait until any thread finishes?

CodePudding user response：

Locust uses gevent which makes I/O asyncronous. A single Locust/Python process can only use one CPU thread (a slight oversimplification), but it can make concurrent HTTP requests: When a request is made by one user, control is immediately handed over to other running users, which can in turn trigger other requests.

This is fundamentally different from Java (which is threaded but often synchronous), but similar to JavaScript.

As long as you run enough Locust worker processes, this is a very efficient approach, and a single process can handle thousands of concurrent users (in fact, the number of users is almost never a limitation - the number of requests per second is the limiting factor)

See Locust's documentation (https://docs.locust.io/en/stable/running-locust-distributed.html)

Because Python cannot fully utilize more than one core per process (see GIL), you should typically run one worker instance per processor core on the worker machines in order to utilize all their computing power.