On Mon, Oct 26, 2015 at 5:52 AM, Jan Kara <j...@suse.com> wrote: > This patch implements a mechanism where after printing specified number > of characters (tunable as a kernel parameter printk.offload_chars), CPU > doing printing asks for help by waking up one of dedicated kthreads. As > soon as the printing CPU notices kthread got scheduled and is spinning > on print_lock dedicated for that purpose, it drops console_sem, > print_lock, and exits console_unlock(). Kthread then takes over printing > instead. This way no CPU should spend printing too long even if there > is heavy printk traffic.
> +/* > + * Number of kernel threads for offloading printing. We need at least two so > + * that they can hand over printing from one to another one and thus switch > + * CPUs. > + */ > +#define PRINTING_TASKS 2 > + > +/* Wait queue printing kthreads sleep on when idle */ > +static DECLARE_WAIT_QUEUE_HEAD(print_queue); Having two tasks, not one, for printking for the case when console output is slow... sounds wasteful. Can this be improved so that only one task is needed?
