http://lists.gnu.org/archive/html/qemu-devel/2004-07/msg00279.html
but I can't see how to get rid of it and still check for redundant
updates in NxN pixel blocks (N=32 by default). The point of checking
NxN squares is that mouse pointer pixmaps are square and so the most
common display updates - mouse pointer movements - are often reduced
to transmission of a single 32x32 block using this strategy.
The shadow framebuffer is only allocated when -remote-x11 is present,
so the patch has no effect on default memory use.
I measured the bandwidth saving roughly by resuming a vm snapshot
containing a web browser showing a page with a lot of links. I moved
the pointer slowly over the links (so they change colour) and scrolled
up and down a bit; about 1/2 minute of activity in total. I tried to do
the same with and without -remote-x11. Without -remote-x11, 163Mbyte
was transmitted to the X server; with it, 20.6Mbyte was, about an 8:1
reduction.
J
diff -u -r Orig/qemu-0.9.0/sdl.c qemu-0.9.0/sdl.c
--- Orig/qemu-0.9.0/sdl.c 2007-02-05 23:01:54.000000000 +0000
+++ qemu-0.9.0/sdl.c 2007-03-13 22:16:40.000000000 +0000
@@ -29,6 +29,8 @@
#include <signal.h>
#endif
+#include <assert.h>
+
static SDL_Surface *screen;
static int gui_grab; /* if true, all keyboard/mouse events are grabbed */
static int last_vm_running;
@@ -44,17 +46,232 @@
static SDL_Cursor *sdl_cursor_hidden;
static int absolute_enabled = 0;
+/* Mechanism to reduce the total amount of data transmitted to the X
+ server, often quite dramatically. Keep a shadow copy of video
+ memory in alt_pixels, and when asked to update a rectangle, use
+ the shadow copy to establish areas which are the same, and so do
+ not need updating.
+*/
+
+static void* alt_pixels = NULL;
+
+#define THRESH 32
+
+/* Return 1 if the area [x .. x+w-1, y .. y+w-1] is different from
+ the old version and so needs updating. */
+static int cmpArea_16bit ( int x, int y, int w, int h )
+{
+ int i, j;
+ unsigned int sll;
+ unsigned short* p1base = (unsigned short*)screen->pixels;
+ unsigned short* p2base = (unsigned short*)alt_pixels;
+ assert(screen->format->BytesPerPixel == 2);
+ if (w == 0 || h == 0)
+ return 0;
+ assert(w > 0 && h > 0);
+ sll = ((unsigned int)screen->pitch) >> 1;
+ for (j = y; j < y+h; j++) {
+ unsigned short* p1p = & p1base[j * sll + x];
+ unsigned short* p2p = & p2base[j * sll + x];
+ for (i = 0; i < w-5; i += 5) {
+ if (p1p[i+0] != p2p[i+0]) return 1;
+ if (p1p[i+1] != p2p[i+1]) return 1;
+ if (p1p[i+2] != p2p[i+2]) return 1;
+ if (p1p[i+3] != p2p[i+3]) return 1;
+ if (p1p[i+4] != p2p[i+4]) return 1;
+ }
+ for (/*fixup*/; i < w; i++) {
+ if (p1p[i+0] != p2p[i+0]) return 1;
+ }
+ }
+ return 0;
+}
+static void copyArea_16bit ( int x, int y, int w, int h )
+{
+ int i, j;
+ unsigned int sll;
+ unsigned short* p1base = (unsigned short*)screen->pixels;
+ unsigned short* p2base = (unsigned short*)alt_pixels;
+ assert(screen->format->BytesPerPixel == 2);
+ sll = ((unsigned int)screen->pitch) >> 1;
+ if (w == 0 || h == 0)
+ return;
+ assert(w > 0 && h > 0);
+ for (j = y; j < y+h; j++) {
+ unsigned short* p1p = & p1base[j * sll + x];
+ unsigned short* p2p = & p2base[j * sll + x];
+ for (i = 0; i < w-5; i += 5) {
+ p2p[i+0] = p1p[i+0];
+ p2p[i+1] = p1p[i+1];
+ p2p[i+2] = p1p[i+2];
+ p2p[i+3] = p1p[i+3];
+ p2p[i+4] = p1p[i+4];
+ }
+ for (/*fixup*/; i < w; i++) {
+ p2p[i+0] = p1p[i+0];
+ }
+ }
+}
+
+static int cmpArea_32bit ( int x, int y, int w, int h )
+{
+ int i, j;
+ unsigned int sll;
+ unsigned int* p1base = (unsigned int*)screen->pixels;
+ unsigned int* p2base = (unsigned int*)alt_pixels;
+ assert(screen->format->BytesPerPixel == 4);
+ sll = ((unsigned int)screen->pitch) >> 2;
+ for (j = y; j < y+h; j++) {
+ for (i = x; i < x+w; i++) {
+ if (p1base [j * sll +i] != p2base [j * sll +i])
+ return 1;
+ }
+ }
+ return 0;
+}
+static void copyArea_32bit ( int x, int y, int w, int h )
+{
+ int i, j;
+ unsigned int sll;
+ unsigned int* p1base = (unsigned int*)screen->pixels;
+ unsigned int* p2base = (unsigned int*)alt_pixels;
+ assert(screen->format->BytesPerPixel == 4);
+ sll = ((unsigned int)screen->pitch) >> 2;
+ for (j = y; j < y+h; j++) {
+ for (i = x; i < x+w; i++) {
+ p2base [j * sll +i] = p1base [j * sll +i];
+ }
+ }
+}
+
+
+static void econoUpdate (DisplayState *ds, int x, int y,
+ unsigned int w, unsigned int h)
+{
+ static int tested_total = 0;
+ static int update_total = 0;
+
+ int (*cmpArea) (int, int, int, int) = NULL;
+ void (*copyArea)(int, int, int, int) = NULL;
+
+ int xi, xj, xlim, yi, yj, ylim, ntest, nupd;
+ if (w == 0 || h == 0)
+ return;
+
+ if (screen->format->BytesPerPixel == 4) {
+ cmpArea = cmpArea_32bit;
+ copyArea = copyArea_32bit;
+ }
+ else
+ if (screen->format->BytesPerPixel == 2) {
+ cmpArea = cmpArea_16bit;
+ copyArea = copyArea_16bit;
+ }
+ else
+ assert(0); /* should not be reached - sdl_update guards against this */
+
+ xlim = x + w;
+ ylim = y + h;
+
+ ntest = nupd = 0;
+ for (xi = x; xi < xlim; xi += THRESH) {
+ xj = xi + THRESH;
+ if (xj > xlim) xj = xlim;
+ for (yi = y; yi < ylim; yi += THRESH) {
+ yj = yi + THRESH;
+ if (yj > ylim) yj = ylim;
+ if (xj-xi == 0 || yj-yi == 0)
+ continue;
+ ntest++;
+ if (cmpArea(xi, yi, xj-xi, yj-yi)) {
+ nupd++;
+ copyArea(xi, yi, xj-xi, yj-yi);
+ SDL_UpdateRect(screen, xi, yi, xj-xi, yj-yi);
+ }
+ }
+ }
+ tested_total += ntest;
+ update_total += nupd;
+ if (0)
+ printf("(tested, updated): total (%d, %d), this time (%d, %d)\n",
+ tested_total, update_total, ntest, nupd);
+}
+
+
static void sdl_update(DisplayState *ds, int x, int y, int w, int h)
{
- // printf("updating x=%d y=%d w=%d h=%d\n", x, y, w, h);
- SDL_UpdateRect(screen, x, y, w, h);
+ int warned = 0;
+
+ //printf("updating x=%d y=%d w=%d h=%d\n", x, y, w, h);
+ // printf("Total Size %d %d\n", screen->w, screen->h);
+ //printf("BytesPerPixel %d\n", screen->format->BytesPerPixel);
+ //printf("pitch %d (%d)\n", screen->pitch,
+ // screen->w * screen->format->BytesPerPixel);
+
+ if (!remote_x11) {
+ SDL_UpdateRect(screen, x, y, w, h);
+ return;
+ }
+
+ if ( (screen->format->BytesPerPixel != 4
+ && screen->format->BytesPerPixel != 2)
+ || screen->pitch != screen->w * screen->format->BytesPerPixel) {
+ if (!warned) {
+ warned = 1;
+ fprintf(stderr, "qemu: SDL update optimisation disabled\n"
+ " (wrong bits-per-pixel, or wrong pitch)\n");
+ }
+ SDL_UpdateRect(screen, x, y, w, h);
+ return;
+ }
+
+ assert(screen->pitch == screen->w * screen->format->BytesPerPixel);
+ assert(sizeof(int) == 4);
+ assert(sizeof(short) == 2);
+ if (alt_pixels == NULL) {
+ /* First time through (at this resolution).
+ Copy entire screen. */
+ if (screen->format->BytesPerPixel == 4) {
+ int i, word32s = screen->w * screen->h;
+ if (0) printf("copying init screen - 32 bit\n");
+ alt_pixels = malloc(word32s * sizeof(int));
+ assert(alt_pixels);
+ for (i = 0; i < word32s; i++)
+ ((unsigned int*)alt_pixels)[i]
+ = ((unsigned int*)(screen->pixels))[i];
+ SDL_UpdateRect(screen, x, y, w, h);
+ if (0) printf("done- 32 bit\n");
+ }
+ else
+ if (screen->format->BytesPerPixel == 2) {
+ int i, word16s = screen->w * screen->h;
+ if (0) printf("copying init screen - 16 bit\n");
+ alt_pixels = malloc(word16s * sizeof(int));
+ assert(alt_pixels);
+ for (i = 0; i < word16s; i++)
+ ((unsigned short*)alt_pixels)[i]
+ = ((unsigned short*)(screen->pixels))[i];
+ SDL_UpdateRect(screen, x, y, w, h);
+ if (0) printf("done - 16 bit\n");
+ }
+ else
+ assert(0); /* guarded above */
+ } else {
+ assert(w >= 0);
+ assert(h >= 0);
+ econoUpdate(ds, x, y, w, h);
+ }
}
static void sdl_resize(DisplayState *ds, int w, int h)
{
int flags;
- // printf("resizing to %d %d\n", w, h);
+ if (alt_pixels) {
+ assert(remote_x11);
+ free(alt_pixels);
+ alt_pixels = NULL;
+ }
flags = SDL_HWSURFACE|SDL_ASYNCBLIT|SDL_HWACCEL;
if (gui_fullscreen)
diff -u -r Orig/qemu-0.9.0/vl.c qemu-0.9.0/vl.c
--- Orig/qemu-0.9.0/vl.c 2007-02-05 23:01:54.000000000 +0000
+++ qemu-0.9.0/vl.c 2007-03-13 22:12:39.000000000 +0000
@@ -173,6 +173,7 @@
int nb_option_roms;
int semihosting_enabled = 0;
int autostart = 1;
+int remote_x11 = 0;
/***********************************************************/
/* x86 ISA bus support */
@@ -6121,6 +6122,7 @@
"-vnc display start a VNC server on display\n"
#ifndef _WIN32
"-daemonize daemonize QEMU after initializing\n"
+ "-remote-x11 improve graphics responsiveness when X11
client != server\n"
#endif
"-option-rom rom load a file, rom, into the option ROM space\n"
"\n"
@@ -6204,6 +6206,7 @@
QEMU_OPTION_no_acpi,
QEMU_OPTION_no_reboot,
QEMU_OPTION_daemonize,
+ QEMU_OPTION_remote_x11,
QEMU_OPTION_option_rom,
QEMU_OPTION_semihosting
};
@@ -6288,6 +6291,7 @@
{ "no-acpi", 0, QEMU_OPTION_no_acpi },
{ "no-reboot", 0, QEMU_OPTION_no_reboot },
{ "daemonize", 0, QEMU_OPTION_daemonize },
+ { "remote-x11", 0, QEMU_OPTION_remote_x11 },
{ "option-rom", HAS_ARG, QEMU_OPTION_option_rom },
#if defined(TARGET_ARM)
{ "semihosting", 0, QEMU_OPTION_semihosting },
@@ -6947,6 +6951,9 @@
case QEMU_OPTION_daemonize:
daemonize = 1;
break;
+ case QEMU_OPTION_remote_x11:
+ remote_x11 = 1;
+ break;
case QEMU_OPTION_option_rom:
if (nb_option_roms >= MAX_OPTION_ROMS) {
fprintf(stderr, "Too many option ROMs\n");
diff -u -r Orig/qemu-0.9.0/vl.h qemu-0.9.0/vl.h
--- Orig/qemu-0.9.0/vl.h 2007-02-05 23:01:54.000000000 +0000
+++ qemu-0.9.0/vl.h 2007-03-13 22:11:24.000000000 +0000
@@ -159,6 +159,7 @@
extern int no_quit;
extern int semihosting_enabled;
extern int autostart;
+extern int remote_x11;
#define MAX_OPTION_ROMS 16
extern const char *option_rom[MAX_OPTION_ROMS];
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