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From
SubjectRe: Multiple monitors
Pavel Machek wrote:
> > On one 686 class machine, I saw text mode take nearly two seconds to
> > scroll the screen, when all but one line of the screen was being
> > scrolled (so it had to copy everything). This was in pure text mode,
> > not even a framebuffer! In X it was invisibly fast.
>
> 2 seconds on vga console is way too much. It could happen with
> framebuffer + usb hogging PCI...

No, this was in 1996 on a Pentium Pro machine, with no USB or x86
framebuffer drivers even written then :-) It was plain 80x50 text mode,
really.

I still have the patch I wrote in March 1997 (attached for reference),
and this patch made a _huge_ difference to text mode Emacs on those
machines. An equivalent fix seems to have been incorporated in
console.c by now.

enjoy,
-- Jamie

--- linux/drivers/char/console.c.dist Tue Jan 14 22:01:17 1997
+++ linux/drivers/char/console.c Tue Feb 25 03:40:26 1997
@@ -592,15 +592,22 @@
__set_origin(__real_origin);
}

-void scrup(int currcons, unsigned int t, unsigned int b)
+static void scrup(int currcons, unsigned int t, unsigned int b, unsigned int nr)
{
int hardscroll = hardscroll_enabled;

- if (b > video_num_lines || t >= b)
+ if (b > video_num_lines || t >= b || nr == 0)
return;
+ if (nr > b - t)
+ nr = b - t;
if (t || b != video_num_lines)
hardscroll = 0;
if (hardscroll) {
+ if (nr != 1) {
+ while (nr--)
+ scrup (currcons, t, b, 1);
+ return;
+ }
origin += video_size_row;
pos += video_size_row;
scr_end += video_size_row;
@@ -639,14 +646,14 @@
set_origin(currcons);
} else {
unsigned short * d = (unsigned short *) (origin+video_size_row*t);
- unsigned short * s = (unsigned short *) (origin+video_size_row*(t+1));
- unsigned int count = (b-t-1) * video_num_columns;
+ unsigned short * s = (unsigned short *) (origin+video_size_row*(t+nr));
+ unsigned int count = (b-t-nr) * video_num_columns;

while (count) {
count--;
scr_writew(scr_readw(s++), d++);
}
- count = video_num_columns;
+ count = nr*video_num_columns;
while (count) {
count--;
scr_writew(video_erase_char, d++);
@@ -654,27 +661,28 @@
}
}

-void
-scrdown(int currcons, unsigned int t, unsigned int b)
+static void
+scrdown(int currcons, unsigned int t, unsigned int b, unsigned int nr)
{
unsigned short *d, *s;
unsigned int count;

- if (b > video_num_lines || t >= b)
+ if (b > video_num_lines || t >= b || nr == 0)
return;
+ if (nr > b - t)
+ nr = b - t;
d = (unsigned short *) (origin+video_size_row*b);
- s = (unsigned short *) (origin+video_size_row*(b-1));
- count = (b-t-1)*video_num_columns;
+ s = (unsigned short *) (origin+video_size_row*(b-nr));
+ count = (b-t-nr)*video_num_columns;
while (count) {
count--;
scr_writew(scr_readw(--s), --d);
}
- count = video_num_columns;
+ count = nr*video_num_columns;
while (count) {
count--;
scr_writew(video_erase_char, --d);
}
- has_scrolled = 1;
}

static void lf(int currcons)
@@ -683,7 +691,7 @@
* if below scrolling region
*/
if (y+1 == bottom)
- scrup(currcons,top,bottom);
+ scrup(currcons,top,bottom,1);
else if (y < video_num_lines-1) {
y++;
pos += video_size_row;
@@ -697,7 +705,7 @@
* if above scrolling region
*/
if (y == top)
- scrdown(currcons,top,bottom);
+ scrdown(currcons,top,bottom,1);
else if (y > 0) {
y--;
pos -= video_size_row;
@@ -1171,84 +1179,61 @@
}
}

-static void insert_char(int currcons)
+static void insert_chars(int currcons, unsigned int nr)
{
- unsigned int i = x;
- unsigned short tmp, old = video_erase_char;
+ unsigned int count;
unsigned short * p = (unsigned short *) pos;

- while (i++ < video_num_columns) {
- tmp = scr_readw(p);
- scr_writew(old, p);
- old = tmp;
- p++;
+ if (nr >= video_num_columns - x)
+ nr = video_num_columns - x;
+ if (nr == 0)
+ return;
+
+ p += video_num_columns - x;
+ count = video_num_columns - x - nr;
+ while (count--) {
+ p--;
+ scr_writew(scr_readw(p-nr), p);
}
+ count = nr;
+ while (count--)
+ scr_writew(video_erase_char, --p);
+
need_wrap = 0;
}

-static void insert_line(int currcons)
+static inline void insert_lines(int currcons, unsigned int nr)
{
- scrdown(currcons,y,bottom);
+ scrdown(currcons,y,bottom,nr);
need_wrap = 0;
}

-static void delete_char(int currcons)
+static void delete_chars(int currcons, unsigned int nr)
{
- unsigned int i = x;
+ unsigned int count;
unsigned short * p = (unsigned short *) pos;

- while (++i < video_num_columns) {
- scr_writew(scr_readw(p+1), p);
+ if (nr >= video_num_columns - x)
+ nr = video_num_columns - x;
+ if (nr == 0)
+ return;
+
+ count = video_num_columns - x - nr;
+ while (count--) {
+ scr_writew(scr_readw(p+nr), p);
p++;
}
- scr_writew(video_erase_char, p);
- need_wrap = 0;
-}
+ count = nr;
+ while (count--)
+ scr_writew(video_erase_char, p++);

-static void delete_line(int currcons)
-{
- scrup(currcons,y,bottom);
need_wrap = 0;
}

-static void csi_at(int currcons, unsigned int nr)
-{
- if (nr > video_num_columns)
- nr = video_num_columns;
- else if (!nr)
- nr = 1;
- while (nr--)
- insert_char(currcons);
-}
-
-static void csi_L(int currcons, unsigned int nr)
-{
- if (nr > video_num_lines)
- nr = video_num_lines;
- else if (!nr)
- nr = 1;
- while (nr--)
- insert_line(currcons);
-}
-
-static void csi_P(int currcons, unsigned int nr)
-{
- if (nr > video_num_columns)
- nr = video_num_columns;
- else if (!nr)
- nr = 1;
- while (nr--)
- delete_char(currcons);
-}
-
-static void csi_M(int currcons, unsigned int nr)
+static inline void delete_lines(int currcons, unsigned int nr)
{
- if (nr > video_num_lines)
- nr = video_num_lines;
- else if (!nr)
- nr=1;
- while (nr--)
- delete_line(currcons);
+ scrup(currcons,y,bottom,nr);
+ need_wrap = 0;
}

static void save_cur(int currcons)
@@ -1468,7 +1453,7 @@
lf(currcons);
}
if (decim)
- insert_char(currcons);
+ insert_chars(currcons, 1);
scr_writew( video_mode_512ch ?
((attr & 0xf7) << 8) + ((tc & 0x100) << 3) +
(tc & 0x0ff) : (attr << 8) + tc,
@@ -1707,13 +1692,13 @@
csi_K(currcons,par[0]);
continue;
case 'L':
- csi_L(currcons,par[0]);
+ insert_lines(currcons,(par[0] ? par[0] : 1));
continue;
case 'M':
- csi_M(currcons,par[0]);
+ delete_lines(currcons,(par[0] ? par[0] : 1));
continue;
case 'P':
- csi_P(currcons,par[0]);
+ delete_chars(currcons,(par[0] ? par[0] : 1));
continue;
case 'c':
if (!par[0])
@@ -1762,7 +1747,7 @@
csi_X(currcons, par[0]);
continue;
case '@':
- csi_at(currcons,par[0]);
+ insert_chars(currcons,(par[0] ? par[0] : 1));
continue;
case ']': /* setterm functions */
setterm_command(currcons);
--- linux/drivers/char/vt.c.dist Wed Feb 5 20:04:38 1997
+++ linux/drivers/char/vt.c Tue Feb 25 03:42:23 1997
@@ -28,6 +28,7 @@
#include "vt_kern.h"
#include "diacr.h"
#include "selection.h"
+#include "console_struct.h" /* for `vc_has_scrolled' */

extern char vt_dont_switch;
extern struct tty_driver console_driver;
@@ -299,9 +300,10 @@
/*
* explicitly blank/unblank the screen if switching modes
*/
- if (arg == KD_TEXT)
+ if (arg == KD_TEXT) {
+ vc_cons[console].d->vc_has_scrolled = 1;
do_unblank_screen();
- else
+ } else
do_blank_screen(1);
return 0;

-
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