Write stall activation criteria for mutable memtable memory limits

When configuring RocksDB, the write stall mechanism is designed to pause writes when memory pressure from mutable memtables exceeds configured limits. The documentation states that a stall occurs if the total memory used by all mutable memtables surpasses write_buffer_limit or if the number of immutable memtables awaiting flush reaches max_write_buffer_number. However, it is unclear whether the stall evaluation considers the aggregate size of mutable memtables only, or also checks each individual memtable against write_buffer_size. Additionally, the interaction between max_write_buffer_number and min_write_buffer_number_to_merge in triggering stalls is not explicitly detailed.

Understanding the precise condition that initiates a stall is important for tuning write throughput without risking out‑of‑memory situations.

Does the stall trigger when the cumulative size of all mutable memtables exceeds write_buffer_limit, regardless of the size of any single memtable?
Does max_write_buffer_number influence the stall threshold independently of total memtable memory?
Is the stall condition evaluated per memtable or only on the aggregate mutable memtable usage?