How many WorkRequests a multiplex worker process may receive in parallel if you use the 'worker' strategy with --worker_multiplex. May be specified as [name=value] to give a different value per mnemonic. The limit is based on worker keys, which are differentiated based on mnemonic, but also on startup flags and environment, so there can in some cases be more workers per mnemonic than this flag specifies. Takes an integer, or a keyword ("auto", "HOST_CPUS", "HOST_RAM"), optionally followed by an operation ([- |*]<float>) eg. "auto", "HOST_CPUS*.5". 'auto' calculates a reasonable default based on machine capacity. "=value" sets a default for unspecified mnemonics.