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

Linus Torvalds
2009-10-13T15:41:23Z

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