Merge branch 'docs-clarify-resource-boundaries' into 'master'

Prefer memory bound to CPU bound if a worker is both

Closes #207186

See merge request gitlab-org/gitlab!25517

doc/development/sidekiq_style_guide.md

@@ -167,7 +167,7 @@ Most workers tend to spend most of their time blocked, wait on network responses
 from other services such as Redis, Postgres and Gitaly. Since Sidekiq is a
 multithreaded environment, these jobs can be scheduled with high concurrency.
 
-Some workers, however, spend large amounts of time _on-cpu_ running logic in
+Some workers, however, spend large amounts of time _on-CPU_ running logic in
 Ruby. Ruby MRI does not support true multithreading - it relies on the
 [GIL](https://thoughtbot.com/blog/untangling-ruby-threads#the-global-interpreter-lock)
 to greatly simplify application development by only allowing one section of Ruby
@@ -187,13 +187,17 @@ performance.
 Likewise, if a worker uses large amounts of memory, we can run these on a
 bespoke low concurrency, high memory fleet.
 
-Note that Memory-bound workers create heavy GC workloads, with pauses of
+Note that memory-bound workers create heavy GC workloads, with pauses of
 10-50ms. This will have an impact on the latency requirements for the
 worker. For this reason, `memory` bound, `latency_sensitive` jobs are not
 permitted and will fail CI. In general, `memory` bound workers are
 discouraged, and alternative approaches to processing the work should be
 considered.
 
+If a worker needs large amounts of both memory and CPU time, it should be marked as
+memory-bound, due to the above restrction on latency-sensitive memory-bound
+workers.
+
 ## Declaring a Job as CPU-bound
 
 This example shows how to declare a job as being CPU-bound.