On Thu 2017-06-29 16:56:30, Sergey Senozhatsky wrote: > yeah, I agree and understand that per-CPU printk kthreads > is a bit... too much. > > it was just a quick idea and I just gave it a try. but there > are some potential takeaways from the series (not sure if you > looked at the last patches of the series). > > with per-CPU kthreads we easily > > 1) can be quite flexible > there can be only certain CPUs that will take over printing duty. > so if you system has, say, IRQ affinity set up or anything else > that is critical, you can forbid printk offloading to those CPUs. > so "important" CPUs will not print out more than atomic_limit chars, > the rest of the job will be handled by "less important" CPUs. > > * this can be achieved with a single printk kthread. > but still, that's something I haven't thought about before this > series.
Sounds interesting. Well, I would prefer to leave this for further optimization. It is a completely new area and it might open another can of worms. > 2) can offload printing to other CPUs from vprintk_emit() > and avoid any of scheduler->timekeeping->etc. paths. which will > replace printk_deferred(). I probably miss something. There is still called wake_up_process() in this patchset and we could not do this in some scheduler and timekeeping paths. Also we must not take the console_lock() in these paths because it calls wake_up_process() as well. But we want to flush few lines when possible. Best Regards, Petr
