[PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check

[PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check

[André Goddard Rosa]

>From fd3098fe2764b049e23ea125a20979410699d257 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9=20Goddard=20Rosa?= <andre.goddard@gmail.com>
Date: Sun, 1 Nov 2009 13:46:26 -0200
Subject: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

   text    data     bss     dec     hex filename
  15735       0       8   15743    3d7f lib/vsprintf.o-before
  15719       0       8   15727    3d6f lib/vsprintf.o-minus-double-check

Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>
---
 lib/vsprintf.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 14e4197..af79152 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -747,8 +747,9 @@ static char *ip6_compressed_string(char *p, const
char *addr)
 				p = pack_hex_byte(p, hi);
 			else
 				*p++ = hex_asc_lo(hi);
+			p = pack_hex_byte(p, lo);
 		}
-		if (hi || lo > 0x0f)
+		else if (lo > 0x0f)
 			p = pack_hex_byte(p, lo);
 		else
 			*p++ = hex_asc_lo(lo);
-- 
1.6.5.2.140.g5f809

Re: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check

[Frederic Weisbecker]

On Mon, Nov 02, 2009 at 03:26:36PM -0200, André Goddard Rosa wrote:
> From fd3098fe2764b049e23ea125a20979410699d257 Mon Sep 17 00:00:00 2001
> From: =?UTF-8?q?Andr=C3=A9=20Goddard=20Rosa?= <andre.goddard@gmail.com>
> Date: Sun, 1 Nov 2009 13:46:26 -0200
> Subject: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
> 
>    text    data     bss     dec     hex filename
>   15735       0       8   15743    3d7f lib/vsprintf.o-before
>   15719       0       8   15727    3d6f lib/vsprintf.o-minus-double-check
> 
> Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>



Please add a changelog in your patches, I mean something that
explain your practical change.

I'm not sure this change is necessary, the only impact is a small
reduce of binary code. Well, why not.


> ---
>  lib/vsprintf.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 14e4197..af79152 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -747,8 +747,9 @@ static char *ip6_compressed_string(char *p, const
> char *addr)
>  				p = pack_hex_byte(p, hi);
>  			else
>  				*p++ = hex_asc_lo(hi);
> +			p = pack_hex_byte(p, lo);
>  		}
> -		if (hi || lo > 0x0f)
> +		else if (lo > 0x0f)
>  			p = pack_hex_byte(p, lo);
>  		else
>  			*p++ = hex_asc_lo(lo);
> -- 
> 1.6.5.2.140.g5f809

Re: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check

[Joe Perches]

On Mon, 2009-11-02 at 19:19 +0100, Frederic Weisbecker wrote:
> On Mon, Nov 02, 2009 at 03:26:36PM -0200, André Goddard Rosa wrote:
> > Subject: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check
> >    text    data     bss     dec     hex filename
> >   15735       0       8   15743    3d7f lib/vsprintf.o-before
> >   15719       0       8   15727    3d6f lib/vsprintf.o-minus-double-check
> Please add a changelog in your patches, I mean something that
> explain your practical change.

Read the subject and try not to go overboard.
I think the changelog André provided is perfect.

Re: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check

[Frederic Weisbecker]

On Mon, Nov 02, 2009 at 10:29:43AM -0800, Joe Perches wrote:
> On Mon, 2009-11-02 at 19:19 +0100, Frederic Weisbecker wrote:
> > On Mon, Nov 02, 2009 at 03:26:36PM -0200, André Goddard Rosa wrote:
> > > Subject: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check
> > >    text    data     bss     dec     hex filename
> > >   15735       0       8   15743    3d7f lib/vsprintf.o-before
> > >   15719       0       8   15727    3d6f lib/vsprintf.o-minus-double-check
> > Please add a changelog in your patches, I mean something that
> > explain your practical change.
> 
> Read the subject and try not to go overboard.
> I think the changelog André provided is perfect.


It took me some time yesterday to understand how ip6_compressed_string()
does its job, hence it took me some time to ensure this patch is safe,
hence this reaction for something that didn't seem obvious to me at
a first glance.

But you're right actually, the problem was more in my homework than in
the changelog.

Re: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check

[Ingo Molnar]

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> On Mon, Nov 02, 2009 at 10:29:43AM -0800, Joe Perches wrote:
> > On Mon, 2009-11-02 at 19:19 +0100, Frederic Weisbecker wrote:
> > > On Mon, Nov 02, 2009 at 03:26:36PM -0200, André Goddard Rosa wrote:
> > > > Subject: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check
> > > >    text    data     bss     dec     hex filename
> > > >   15735       0       8   15743    3d7f lib/vsprintf.o-before
> > > >   15719       0       8   15727    3d6f lib/vsprintf.o-minus-double-check
> > > Please add a changelog in your patches, I mean something that
> > > explain your practical change.
> > 
> > Read the subject and try not to go overboard.
> > I think the changelog André provided is perfect.
> 
> 
> It took me some time yesterday to understand how 
> ip6_compressed_string() does its job, hence it took me some time to 
> ensure this patch is safe, hence this reaction for something that 
> didn't seem obvious to me at a first glance.
> 
> But you're right actually, the problem was more in my homework than in 
> the changelog.

Since you wrote the last iteration of that bit and you didnt find it 
trivial i'd strongly suggest the next version of this patch to include a 
more verbose changelog that explains what is being done. There's no harm 
in being verbose about reasons for a change - and there's a lot of harm 
from being too short.

	Ingo

Re: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check

[Frederic Weisbecker]

On Mon, Nov 02, 2009 at 08:36:23PM +0100, Ingo Molnar wrote:
> 
> * Frederic Weisbecker <fweisbec@gmail.com> wrote:
> 
> > On Mon, Nov 02, 2009 at 10:29:43AM -0800, Joe Perches wrote:
> > > On Mon, 2009-11-02 at 19:19 +0100, Frederic Weisbecker wrote:
> > > > On Mon, Nov 02, 2009 at 03:26:36PM -0200, André Goddard Rosa wrote:
> > > > > Subject: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check
> > > > >    text    data     bss     dec     hex filename
> > > > >   15735       0       8   15743    3d7f lib/vsprintf.o-before
> > > > >   15719       0       8   15727    3d6f lib/vsprintf.o-minus-double-check
> > > > Please add a changelog in your patches, I mean something that
> > > > explain your practical change.
> > > 
> > > Read the subject and try not to go overboard.
> > > I think the changelog André provided is perfect.
> > 
> > 
> > It took me some time yesterday to understand how 
> > ip6_compressed_string() does its job, hence it took me some time to 
> > ensure this patch is safe, hence this reaction for something that 
> > didn't seem obvious to me at a first glance.
> > 
> > But you're right actually, the problem was more in my homework than in 
> > the changelog.
> 
> Since you wrote the last iteration of that bit and you didnt find it 


André wrote this patch, not me :)


> trivial i'd strongly suggest the next version of this patch to include a 
> more verbose changelog that explains what is being done. There's no harm 
> in being verbose about reasons for a change - and there's a lot of harm 
> from being too short.
> 
> 	Ingo

Re: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check

[Ingo Molnar]

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> On Mon, Nov 02, 2009 at 08:36:23PM +0100, Ingo Molnar wrote:
> > 
> > * Frederic Weisbecker <fweisbec@gmail.com> wrote:
> > 
> > > On Mon, Nov 02, 2009 at 10:29:43AM -0800, Joe Perches wrote:
> > > > On Mon, 2009-11-02 at 19:19 +0100, Frederic Weisbecker wrote:
> > > > > On Mon, Nov 02, 2009 at 03:26:36PM -0200, André Goddard Rosa wrote:
> > > > > > Subject: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check
> > > > > >    text    data     bss     dec     hex filename
> > > > > >   15735       0       8   15743    3d7f lib/vsprintf.o-before
> > > > > >   15719       0       8   15727    3d6f lib/vsprintf.o-minus-double-check
> > > > > Please add a changelog in your patches, I mean something that
> > > > > explain your practical change.
> > > > 
> > > > Read the subject and try not to go overboard.
> > > > I think the changelog André provided is perfect.
> > > 
> > > 
> > > It took me some time yesterday to understand how 
> > > ip6_compressed_string() does its job, hence it took me some time to 
> > > ensure this patch is safe, hence this reaction for something that 
> > > didn't seem obvious to me at a first glance.
> > > 
> > > But you're right actually, the problem was more in my homework than in 
> > > the changelog.
> > 
> > Since you wrote the last iteration of that bit and you didnt find it 
> 
> 
> André wrote this patch, not me :)

i know - i mean you touched the vsprintf code last materially.

But i see that there's been this commit since then:

  8a27f7c: lib/vsprintf.c: Add "%pI6c" - print pointer as compressed ipv6 address

which introduced ip6_compressed_string().

	Ingo

Re: [PATCH v2 5/7] vsprintf: reduce code size by avoiding extra check

[Ingo Molnar]

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> I'm not sure this change is necessary, the only impact is a small 
> reduce of binary code. Well, why not.

Small reductions in size are nice too. They counter-act small increases 
in kernel size. (which are way more common unfortunately)

	Ingo