# Actor placement and execution resources **URL:** \ **Category:** Ray Core\ **Created:** [November 21, 2023, 11:10am UTC](https://discuss.ray.io/t/actor-placement-and-execution-resources/12897 "2023-11-21T11:10:49Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![YarShev](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/yarshev/32/638_2.png) [@YarShev](https://discuss.ray.io/u/YarShev)\ **Post date:** [November 21, 2023, 11:10am UTC](https://discuss.ray.io/t/actor-placement-and-execution-resources/12897/1 "2023-11-21T11:10:49Z")
**How severe does this issue affect your experience of using Ray?** - None: Just asking a question out of curiosity Hi there. I just read the document about Ray architecture ([link](https://docs.google.com/document/d/1tBw9A4j62ruI5omIJbMxly-la5w4q_TjyJgJL_jN2fI/preview#heading=h.iyrm5j2gcdoq)), in particular, a paragraph of Resource Management and Scheduling, which say an Actor will request 0 CPU for execution by default but request 1 CPUs for placement. As far as I understand, when creating an actor Ray reserves 1 CPUs for the actor. When executing a method of the actor Ray has to use 1 CPUs for execution. I am confused a little. What does it mean “an Actor will request 0 CPU for execution”? ---
**Author:** ![YarShev](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/yarshev/32/638_2.png) [@YarShev](https://discuss.ray.io/u/YarShev)\ **Post date:** [November 22, 2023, 10:22pm UTC](https://discuss.ray.io/t/actor-placement-and-execution-resources/12897/2 "2023-11-22T22:22:29Z")
@sangcho, could you leave some light here? ---
**Author:** ![YarShev](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/yarshev/32/638_2.png) [@YarShev](https://discuss.ray.io/u/YarShev)\ **Post date:** [November 27, 2023, 9:35am UTC](https://discuss.ray.io/t/actor-placement-and-execution-resources/12897/3 "2023-11-27T09:35:17Z")
@yic, could you leave a comment here? ---
**Author:** ![sangcho](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/sangcho/32/425_2.png) [@sangcho](https://discuss.ray.io/u/sangcho)\ **Post date:** [November 30, 2023, 1:06am UTC](https://discuss.ray.io/t/actor-placement-and-execution-resources/12897/4 "2023-11-30T01:06:46Z")
Hi, maybe the comment there is wrong. Basically, the current mechanism is as follow; 1. When actor is scheduled, it requires 1 CPU 2. Once actor is created, it requires 0 CPU. So this ensures only up to num\_cpus actors can be created at the same time, but you can eventually have unlimited # of actors if you don’t specify num\_cpus. By schduling policy, actors are spread across the cluster by default ---
**Author:** ![YarShev](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/yarshev/32/638_2.png) [@YarShev](https://discuss.ray.io/u/YarShev)\ **Post date:** [November 30, 2023, 10:06am UTC](https://discuss.ray.io/t/actor-placement-and-execution-resources/12897/5 "2023-11-30T10:06:06Z")
Hi @sangcho, thank you for your response. I am a little confused about your second point. Once actor is created, it requires 0 CPU. But neither a remote task nor another actor can’t be scheduled to the worker that already holds the actor created so I think it still requires 1 CPU. Isn’t it so? ---
**Author:** ![sangcho](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/sangcho/32/425_2.png) [@sangcho](https://discuss.ray.io/u/sangcho)\ **Post date:** [December 12, 2023, 4:00am UTC](https://discuss.ray.io/t/actor-placement-and-execution-resources/12897/6 "2023-12-12T04:00:19Z")
> But neither a remote task nor another actor can’t be scheduled to the worker that already holds the actor created It is possible. I think the simple explanation is 1. You can schedule only upto num\_cpus=N actors at the same time. 2. Once actors are created, you can create infinite # of actors on that node. ---
**Author:** ![YarShev](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/yarshev/32/638_2.png) [@YarShev](https://discuss.ray.io/u/YarShev)\ **Post date:** [December 12, 2023, 8:43am UTC](https://discuss.ray.io/t/actor-placement-and-execution-resources/12897/7 "2023-12-12T08:43:17Z")
I mean that if a worker still holds an actor, we can’t schedule neither another actor nor a remote function to that worker. Is it right? ---
**Author:** ![sangcho](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/sangcho/32/425_2.png) [@sangcho](https://discuss.ray.io/u/sangcho)\ **Post date:** [December 12, 2023, 3:16pm UTC](https://discuss.ray.io/t/actor-placement-and-execution-resources/12897/8 "2023-12-12T15:16:03Z")
when you say “worker”, did you mean worker process? you cannot create a new actor to a worker process that already initiated an actor. But ray can have more than num\_cpus worker process (it is not a hard cap) per each node ---
**Author:** ![YarShev](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/yarshev/32/638_2.png) [@YarShev](https://discuss.ray.io/u/YarShev)\ **Post date:** [December 12, 2023, 3:34pm UTC](https://discuss.ray.io/t/actor-placement-and-execution-resources/12897/9 "2023-12-12T15:34:16Z")
> when you say “worker”, did you mean worker process? This is exactly what I mean. > you cannot create a new actor to a worker process that already initiated an actor. But ray can have more than num\_cpus worker process (it is not a hard cap) per each node Thanks, this makes sense to me.