From f23eb2b2b28547fc70df82dd5049eb39bec5ba12 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 22 Mar 2011 16:17:32 -0700 Subject: tty: stop using "delayed_work" in the tty layer Using delayed-work for tty flip buffers ends up causing us to wait for the next tick to complete some actions. That's usually not all that noticeable, but for certain latency-critical workloads it ends up being totally unacceptable. As an extreme case of this, passing a token back-and-forth over a pty will take two ticks per iteration, so even just a thousand iterations will take 8 seconds assuming a common 250Hz configuration. Avoiding the whole delayed work issue brings that ping-pong test-case down to 0.009s on my machine. In more practical terms, this latency has been a performance problem for things like dive computer simulators (simulating the serial interface using the ptys) and for other environments (Alan mentions a CP/M emulator). Reported-by: Jef Driesen Acked-by: Greg KH Acked-by: Alan Cox Signed-off-by: Linus Torvalds --- include/linux/kbd_kern.h | 2 +- include/linux/tty.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/kbd_kern.h b/include/linux/kbd_kern.h index 4b0761cc7dd9..ec2d17bc1f1e 100644 --- a/include/linux/kbd_kern.h +++ b/include/linux/kbd_kern.h @@ -159,7 +159,7 @@ static inline void con_schedule_flip(struct tty_struct *t) if (t->buf.tail != NULL) t->buf.tail->commit = t->buf.tail->used; spin_unlock_irqrestore(&t->buf.lock, flags); - schedule_delayed_work(&t->buf.work, 0); + schedule_work(&t->buf.work); } #endif diff --git a/include/linux/tty.h b/include/linux/tty.h index 4e53d4641b38..9f469c700550 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -82,7 +82,7 @@ struct tty_buffer { struct tty_bufhead { - struct delayed_work work; + struct work_struct work; spinlock_t lock; struct tty_buffer *head; /* Queue head */ struct tty_buffer *tail; /* Active buffer */ -- cgit v1.2.3