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

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Date:	Tue, 13 Oct 2009 08:41:23 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Paul Fulghum <paulkf@...rogate.com>
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, 13 Oct 2009, Paul Fulghum wrote:

> 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.

Read the above again. Read what that common sequence is. Please just READ 
the f*cking code, and read my emails, instead of talking about something 
totally different that I'm not talking about at all.

The _most_common_ use of "tty_buffer_request_room()" is literally just the 
above insane sequence I quoted, not the case you talk about at all. Don't 
believe me? Use grep.

What _you_ are talking about is something else, namely the 
tty_prepare_flip stuff. But dammit, that has nothing what-so-ever to do 
with "tty_buffer_request_room()".

What I was pointing out is that there are a lot of 
"tty_buffer_request_room()" calls, and as far as I can see, all of them 
(or at least a large percentage) are just pure and utter crap.

		Linus
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