Hi, On Wed, Sep 27, 2023 at 09:25:54PM +0800, Wang Jinchao wrote: > Hello, I have a few questions about the padata code I've been studying > recently: > > - Why does padata use the WQ_UNBOUND attribute of the workqueue? There's background in this series: https://lore.kernel.org/all/20190813005224.30779-1-daniel.m.jordan@xxxxxxxxxx/ > Because I've noticed a significant maintenance cost related to CPUs. > Are there any specific benefits? Aside from what Steffen said about serialization, the pcrypt cpumasks can be set from sysfs to control where parallel and serial jobs run. > - In what scenarios is it necessary to specify a CPU for serial > execution, or is ensuring the order sufficient? I'm not sure that it's necessary. The way I read it, at least, it seems pcrypt uses cb_cpu to load balance serialization across all CPUs allowed in the serial cpumask.