Commit e052c6d1 authored Oct 17, 2015 by Peter Hurley Committed by Greg Kroah-Hartman Oct 17, 2015

tty: Use unbound workqueue for all input workers



The commonly accepted wisdom that scheduling work on the same cpu
that handled interrupt i/o benefits from cache-locality is only
true if the cpu is idle (since bound kworkers are often the highest
vruntime and thus the lowest priority).

Measurements of scheduling via the unbound queue show lowered
worst-case latency responses of up to 5x over bound workqueue, without
increase in average latency or throughput.

pty i/o test measurements show >3x (!) reduced total running time; tests
previously taking ~8s now complete in <2.5s.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent e176058f

drivers/tty/tty_buffer.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -403,7 +403,7 @@ void tty_schedule_flip(struct tty_port *port)
		* flush_to_ldisc() sees buffer data.
		*/
		smp_store_release(&buf->tail->commit, buf->tail->used);
		schedule_work(&buf->work);
		queue_work(system_unbound_wq, &buf->work);
		}
		EXPORT_SYMBOL(tty_schedule_flip);

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