[PATCH 0/2] vgacon_scrolldelta cleanup

[PATCH 0/2] vgacon_scrolldelta cleanup

[Marcin Slusarz]

[PATCH 1/2] vgacon: optimize scrolling
[PATCH 2/2] vgacon: vgacon_scrolldelta simplification

 drivers/video/console/vgacon.c |   48 ++++++++++++++++++++--------------------
 1 files changed, 24 insertions(+), 24 deletions(-)

[PATCH 1/2] vgacon: optimize scrolling

[Marcin Slusarz]

Join multiple scr_memcpyw into 1-3 calls (usually 2).
(benchmarked average speedup: 1%)

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Antonino Daplas <adaplas@gmail.com>
Cc: linux-fbdev-devel@lists.sourceforge.net
---
 drivers/video/console/vgacon.c |   28 ++++++++++++++++------------
 1 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index bd1f57b..de4f66c 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -292,23 +292,27 @@ static int vgacon_scrolldelta(struct vc_data *c, int lines)
 	d = (void *) c->vc_origin;
 	s = (void *) c->vc_screenbuf;
 
-	while (count--) {
-		scr_memcpyw(d, vgacon_scrollback + soff, c->vc_size_row);
-		d += c->vc_size_row;
-		soff += c->vc_size_row;
-
-		if (soff >= vgacon_scrollback_size)
-			soff = 0;
+	if (count) {
+		int copysize;
+		count *= c->vc_size_row;
+		/* how much memory to end of buffer left? */
+		copysize = min(count, vgacon_scrollback_size - soff);
+		scr_memcpyw(d, vgacon_scrollback + soff, copysize);
+		d += copysize;
+		count -= copysize;
+		
+		if (count) {
+			copysize = min(count, vgacon_scrollback_size);
+			scr_memcpyw(d, vgacon_scrollback, copysize);
+			d += copysize;
+		}
 	}
 
 	if (diff == c->vc_rows) {
 		vgacon_cursor(c, CM_MOVE);
 	} else {
-		while (diff--) {
-			scr_memcpyw(d, s, c->vc_size_row);
-			d += c->vc_size_row;
-			s += c->vc_size_row;
-		}
+		if (diff)
+			scr_memcpyw(d, s, diff * c->vc_size_row);
 	}
 
 	return 1;
-- 
1.5.6.4

[PATCH 2/2] vgacon: vgacon_scrolldelta simplification

[Marcin Slusarz]

There's no point in checking diff == c->vc_rows, because it can be true
only when count == 0, but we already checked that.
Additionally move variables used only in one block to this block.

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Antonino Daplas <adaplas@gmail.com>
Cc: linux-fbdev-devel@lists.sourceforge.net
---
 drivers/video/console/vgacon.c |   22 +++++++++-------------
 1 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index de4f66c..a785f99 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -239,8 +239,7 @@ static void vgacon_restore_screen(struct vc_data *c)
 
 static int vgacon_scrolldelta(struct vc_data *c, int lines)
 {
-	int start, end, count, soff, diff;
-	void *d, *s;
+	int start, end, count, soff;
 
 	if (!lines) {
 		c->vc_visible_origin = c->vc_origin;
@@ -287,13 +286,13 @@ static int vgacon_scrolldelta(struct vc_data *c, int lines)
 	if (count > c->vc_rows)
 		count = c->vc_rows;
 
-	diff = c->vc_rows - count;
-
-	d = (void *) c->vc_origin;
-	s = (void *) c->vc_screenbuf;
-
 	if (count) {
 		int copysize;
+		
+		int diff = c->vc_rows - count;
+		void *d = (void *) c->vc_origin;
+		void *s = (void *) c->vc_screenbuf;
+		
 		count *= c->vc_size_row;
 		/* how much memory to end of buffer left? */
 		copysize = min(count, vgacon_scrollback_size - soff);
@@ -306,14 +305,11 @@ static int vgacon_scrolldelta(struct vc_data *c, int lines)
 			scr_memcpyw(d, vgacon_scrollback, copysize);
 			d += copysize;
 		}
-	}
-
-	if (diff == c->vc_rows) {
-		vgacon_cursor(c, CM_MOVE);
-	} else {
+		
 		if (diff)
 			scr_memcpyw(d, s, diff * c->vc_size_row);
-	}
+	} else
+		vgacon_cursor(c, CM_MOVE);
 
 	return 1;
 }
-- 
1.5.6.4

Re: [Linux-fbdev-devel] [PATCH 1/2] vgacon: optimize scrolling

[Krzysztof Helt]

On Sun, 21 Sep 2008 18:00:08 +0200
Marcin Slusarz <marcin.slusarz@gmail.com> wrote:

> Join multiple scr_memcpyw into 1-3 calls (usually 2).
> (benchmarked average speedup: 1%)
> 

The scr_memcpyw is an inline function so there is no real call here.

However, have you tested the patch with scroll range > 2 *  vgacon_scrollback_size?

It seems that your patch only handles scrolling if it is not bigger than 2 * vgacon_scrollback_size.

Regards,
Krzysztof

> Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
> Cc: Antonino Daplas <adaplas@gmail.com>
> Cc: linux-fbdev-devel@lists.sourceforge.net
> ---
>  drivers/video/console/vgacon.c |   28 ++++++++++++++++------------
>  1 files changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
> index bd1f57b..de4f66c 100644
> --- a/drivers/video/console/vgacon.c
> +++ b/drivers/video/console/vgacon.c
> @@ -292,23 +292,27 @@ static int vgacon_scrolldelta(struct vc_data *c, int lines)
>  	d = (void *) c->vc_origin;
>  	s = (void *) c->vc_screenbuf;
>  
> -	while (count--) {
> -		scr_memcpyw(d, vgacon_scrollback + soff, c->vc_size_row);
> -		d += c->vc_size_row;
> -		soff += c->vc_size_row;
> -
> -		if (soff >= vgacon_scrollback_size)
> -			soff = 0;
> +	if (count) {
> +		int copysize;
> +		count *= c->vc_size_row;
> +		/* how much memory to end of buffer left? */
> +		copysize = min(count, vgacon_scrollback_size - soff);
> +		scr_memcpyw(d, vgacon_scrollback + soff, copysize);
> +		d += copysize;
> +		count -= copysize;
> +		
> +		if (count) {
> +			copysize = min(count, vgacon_scrollback_size);
> +			scr_memcpyw(d, vgacon_scrollback, copysize);
> +			d += copysize;
> +		}
>  	}
>  
>  	if (diff == c->vc_rows) {
>  		vgacon_cursor(c, CM_MOVE);
>  	} else {
> -		while (diff--) {
> -			scr_memcpyw(d, s, c->vc_size_row);
> -			d += c->vc_size_row;
> -			s += c->vc_size_row;
> -		}
> +		if (diff)
> +			scr_memcpyw(d, s, diff * c->vc_size_row);
>  	}
>  
>  	return 1;
> -- 
> 1.5.6.4
> 
> 
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
> Build the coolest Linux based applications with Moblin SDK & win great prizes
> Grand prize is a trip for two to an Open Source event anywhere in the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> _______________________________________________
> Linux-fbdev-devel mailing list
> Linux-fbdev-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-fbdev-devel
> 

----------------------------------------------------------------------
Kredyt Hipoteczny w Banku Millennium - zdobywca Zlotego Lauru Klienta!
Sprawdz >> http://link.interia.pl/f1f15

Re: [Linux-fbdev-devel] [PATCH 1/2] vgacon: optimize scrolling

[Marcin Slusarz]

On Sun, Sep 21, 2008 at 08:37:57PM +0200, Krzysztof Helt wrote:
> On Sun, 21 Sep 2008 18:00:08 +0200
> Marcin Slusarz <marcin.slusarz@gmail.com> wrote:
> 
> > Join multiple scr_memcpyw into 1-3 calls (usually 2).
> > (benchmarked average speedup: 1%)
> > 
> 
> The scr_memcpyw is an inline function so there is no real call here.

... or it's defined to memcpy
 
> However, have you tested the patch with scroll range > 2 *  vgacon_scrollback_size?
>
> It seems that your patch only handles scrolling if it is not bigger than 2 * vgacon_scrollback_size.

No. count is always within range <0, c->vc_rows> (look how it's computed
just before this loop). Second copy is needed only when end of screen
crosses end/beginning of scrollback (it's a circular buffer).

> Regards,
> Krzysztof
> 
> > Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
> > Cc: Antonino Daplas <adaplas@gmail.com>
> > Cc: linux-fbdev-devel@lists.sourceforge.net
> > ---
> >  drivers/video/console/vgacon.c |   28 ++++++++++++++++------------
> >  1 files changed, 16 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
> > index bd1f57b..de4f66c 100644
> > --- a/drivers/video/console/vgacon.c
> > +++ b/drivers/video/console/vgacon.c
> > @@ -292,23 +292,27 @@ static int vgacon_scrolldelta(struct vc_data *c, int lines)
> >  	d = (void *) c->vc_origin;
> >  	s = (void *) c->vc_screenbuf;
> >  
> > -	while (count--) {
> > -		scr_memcpyw(d, vgacon_scrollback + soff, c->vc_size_row);
> > -		d += c->vc_size_row;
> > -		soff += c->vc_size_row;
> > -
> > -		if (soff >= vgacon_scrollback_size)
> > -			soff = 0;
> > +	if (count) {
> > +		int copysize;
> > +		count *= c->vc_size_row;
> > +		/* how much memory to end of buffer left? */
> > +		copysize = min(count, vgacon_scrollback_size - soff);
> > +		scr_memcpyw(d, vgacon_scrollback + soff, copysize);
> > +		d += copysize;
> > +		count -= copysize;
> > +		
> > +		if (count) {
> > +			copysize = min(count, vgacon_scrollback_size);
> > +			scr_memcpyw(d, vgacon_scrollback, copysize);
> > +			d += copysize;
> > +		}
> >  	}
> >  
> >  	if (diff == c->vc_rows) {
> >  		vgacon_cursor(c, CM_MOVE);
> >  	} else {
> > -		while (diff--) {
> > -			scr_memcpyw(d, s, c->vc_size_row);
> > -			d += c->vc_size_row;
> > -			s += c->vc_size_row;
> > -		}
> > +		if (diff)
> > +			scr_memcpyw(d, s, diff * c->vc_size_row);
> >  	}
> >  
> >  	return 1;
> > -- 
> > 1.5.6.4

Re: [Linux-fbdev-devel] [PATCH 1/2] vgacon: optimize scrolling

[Marcin Slusarz]

On Tue, Sep 23, 2008 at 11:59:18PM +0200, Krzysztof Helt wrote:
> On Sun, 21 Sep 2008 23:22:17 +0200
> Marcin Slusarz <marcin.slusarz@gmail.com> wrote:
> 
> > On Sun, Sep 21, 2008 at 08:37:57PM +0200, Krzysztof Helt wrote:
> > > On Sun, 21 Sep 2008 18:00:08 +0200
> > > Marcin Slusarz <marcin.slusarz@gmail.com> wrote:
> > > 
> > > > Join multiple scr_memcpyw into 1-3 calls (usually 2).
> > > > (benchmarked average speedup: 1%)
> > > > 
> > > 
> > > The scr_memcpyw is an inline function so there is no real call here.
> > 
> > ... or it's defined to memcpy
> >  
> > > However, have you tested the patch with scroll range > 2 *  vgacon_scrollback_size?
> > >
> > > It seems that your patch only handles scrolling if it is not bigger than 2 * vgacon_scrollback_size.
> > 
> > No. count is always within range <0, c->vc_rows> (look how it's computed
> > just before this loop). Second copy is needed only when end of screen
> > crosses end/beginning of scrollback (it's a circular buffer).
> > 
> 
> This is not what I asked for. If the vgacon_scrollback_cnt is smaller then c->vc_rows it can happen.
> The answer to my question is that count is always < vgacon_scrollback_cnt (set earlier before 
> checking if it is in the <0,c->vc_rows> range).

Yep

> (...)
> 
> > > > +	if (count) {
> > > > +		int copysize;
> > > > +		count *= c->vc_size_row;
> > > > +		/* how much memory to end of buffer left? */
> > > > +		copysize = min(count, vgacon_scrollback_size - soff);
> > > > +		scr_memcpyw(d, vgacon_scrollback + soff, copysize);
> > > > +		d += copysize;
> > > > +		count -= copysize;
> > > > +		
> > > > +		if (count) {
> > > > +			copysize = min(count, vgacon_scrollback_size);
> 
> This line I got confused by. If the count is always smaller then
> the vgacon_scrollback_cnt before (thus the vgacon_scrollback_size 
> inside the if clause) this line always evaluates to copysize = count here.

You are right. I dropped this "call".
Thanks for a review.

---
Subject: [PATCH 1/2] vgacon: optimize scrolling

Join multiple scr_memcpyw into 1-3 calls (usually 2).
(benchmarked average speedup: 1%)

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: Antonino Daplas <adaplas@gmail.com>
Cc: linux-fbdev-devel@lists.sourceforge.net
---
 drivers/video/console/vgacon.c |   27 +++++++++++++++------------
 1 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index bd1f57b..29d1209 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -292,23 +292,26 @@ static int vgacon_scrolldelta(struct vc_data *c, int lines)
 	d = (void *) c->vc_origin;
 	s = (void *) c->vc_screenbuf;
 
-	while (count--) {
-		scr_memcpyw(d, vgacon_scrollback + soff, c->vc_size_row);
-		d += c->vc_size_row;
-		soff += c->vc_size_row;
-
-		if (soff >= vgacon_scrollback_size)
-			soff = 0;
+	if (count) {
+		int copysize;
+		count *= c->vc_size_row;
+		/* how much memory to end of buffer left? */
+		copysize = min(count, vgacon_scrollback_size - soff);
+		scr_memcpyw(d, vgacon_scrollback + soff, copysize);
+		d += copysize;
+		count -= copysize;
+
+		if (count) {
+			scr_memcpyw(d, vgacon_scrollback, count);
+			d += count;
+		}
 	}
 
 	if (diff == c->vc_rows) {
 		vgacon_cursor(c, CM_MOVE);
 	} else {
-		while (diff--) {
-			scr_memcpyw(d, s, c->vc_size_row);
-			d += c->vc_size_row;
-			s += c->vc_size_row;
-		}
+		if (diff)
+			scr_memcpyw(d, s, diff * c->vc_size_row);
 	}
 
 	return 1;
-- 
1.5.6.4