linux-kernel - Re: [bisected] pty performance problem

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Date:	Mon, 23 Nov 2009 12:48:45 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Mike Galbraith <efault@....de>, Robert Swan <swan.r.l@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [bisected] pty performance problem


* Alan Cox <alan@...rguk.ukuu.org.uk> wrote:

> > diff --git a/drivers/char/tty_buffer.c b/drivers/char/tty_buffer.c
> > index 66fa4e1..92a0864 100644
> > --- a/drivers/char/tty_buffer.c
> > +++ b/drivers/char/tty_buffer.c
> > @@ -495,7 +495,7 @@ void tty_flip_buffer_push(struct tty_struct *tty)
> >  	if (tty->low_latency)
> >  		flush_to_ldisc(&tty->buf.work.work);
> >  	else
> > -		schedule_delayed_work(&tty->buf.work, 1);
> > +		schedule_delayed_work(&tty->buf.work, 0);
> >  }
> >  EXPORT_SYMBOL(tty_flip_buffer_push);
> 
> Another possibility is to do
> 
> 	if (tty->low_latency)
> 		schedule_delayed_work(&tty->buf.work, 0);
> 	else
> 		schedule_delayed_work(&tty->buf.work, 1);

Flaggery for low latency is kind of lame though - especially if it 
defaults to off in most drivers as you say.

	Ingo
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