Messages in this thread | | | From | Valentin Schneider <> | Subject | Re: [RFC PATCH] workqueue: Unbind workers before sending them to exit() | Date | Mon, 25 Jul 2022 11:21:37 +0100 |
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On 22/07/22 19:16, Tejun Heo wrote: > On Thu, Jul 21, 2022 at 02:53:43PM +0100, Valentin Schneider wrote: >> > I think it needs something like task_set_cpumask_possible() which is >> > documented as being usable in (raw) spinlocks and set the task's cpumask >> > to cpu_possible_mask and let the later ttwu help migrate it to a >> > proper non-isolated CPU or let it keep running. >> >> I'll see what I can come up with, thanks for the suggestion. > > Alternatively, we can just kill all the idle kworkers on isolated cpus at > the end of the booting process. >
Hm so my choice of words in the changelog wasn't great - "initial setup" can be kernel init, but *also* setup of whatever workload is being deployed onto the system.
So you can be having "normal" background activity (I've seen some IRQs end up with schedule_work() on isolated CPUs, they're not moved away at boot time but rather shortly before launching the latency-sensitive app), some preliminary stats collection / setup to make sure the CPU will be quiet (e.g. refresh_vm_stats()), and *then* the application starts with fresh-but-no-longer-required extra pcpu kworkers assigned to its CPU.
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