Piotr is right, that depend on the data size you are reading and the memory pressure. Those memory occupied by mmapped region can be recycled and used by other processes if memory pressure is high, that is, other process or service on the same node won't be affected because the OS will recycle the mmapped pages if needed. But currently, you can't assume a bound of the memory can be used, because it will use more memory as long as there is free space and you have more new data to read.
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