linux-kernel - Re: [Bug #14388] keyboard under X with 2.6.31

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Message-Id: <1255447980.3898.3.camel@x2.microgate.com>
Date:	Tue, 13 Oct 2009 10:33:00 -0500
From:	Paul Fulghum <paulkf@...rogate.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, Nix <nix@...eri.org.uk>,
	"Justin P. Mattock" <justinmattock@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Boyan <btanastasov@...oo.co.uk>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Ed Tomlinson <edt@....ca>,
	Frédéric "L. W. Meunier" <fredlwm@...il.com>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Subject: Re: [Bug #14388] keyboard under X with 2.6.31

On Tue, 2009-10-13 at 07:39 -0700, Linus Torvalds wrote:
> It's not a f*cking performance tweak, and you're ludicrous to claim it is. 
> It's pointless, and it's making the code _slower_ rather than faster.
> 
> Lookie here, Alan - the common sequence is crap like this:
> 
> 	tty_buffer_request_room(tty, buf->size);
> 	tty_insert_flip_string(tty, buf->base, buf->size);

The performance tweak of tty_prepare_xxx is that you fill
the tty_buffer directly instead of writing data first to a staging
buffer and then calling tty_insert_flip_string, which just copies
from the staging buffer to the tty_buffer. So it saves a copy operation.
 
--
Paul Fulghum
Microgate Systems, Ltd

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