Make various changes to get a number out of texdown that better

represents realworld usage.  In particular, avoid situations where
the client texture image and the mesa copy (if there is one) are both
resident in L2 cache.

1 files changed, 102 insertions, 31 deletions

diff --git a/progs/demos/texdown.c b/progs/demos/texdown.c
index 96978595b0..91e225d997 100644
--- a/progs/demos/texdown.c
+++ b/progs/demos/texdown.c
@@ -38,8 +38,8 @@
 #include <GL/glut.h>
 
 
-static GLsizei MaxSize = 1024;
-static GLsizei TexWidth = 256, TexHeight = 256, TexBorder = 0;
+static GLsizei MaxSize = 2048;
+static GLsizei TexWidth = 1024, TexHeight = 1024, TexBorder = 0;
 static GLboolean ScaleAndBias = GL_FALSE;
 static GLboolean SubImage = GL_FALSE;
 static GLdouble DownloadRate = 0.0;  /* texels/sec */
@@ -47,6 +47,32 @@ static GLdouble DownloadRate = 0.0;  /* texels/sec */
 static GLuint Mode = 0;
 
 
+/* Try and avoid L2 cache effects by cycling through a small number of
+ * textures.
+ * 
+ * At the initial size of 1024x1024x4 == 4mbyte, say 8 textures will
+ * keep us out of most caches at 32mb total.
+ *
+ * This turns into a fairly interesting question of what exactly you
+ * expect to be in cache in normal usage, and what you think should be
+ * outside.  There's no rules for this, no reason to favour one usage
+ * over another except what the application you care about happens to
+ * resemble most closely.
+ *
+ * - Should the client texture image be in L2 cache?  Has it just been
+ *   generated or read from disk?
+ * - Does the application really use >1 texture, or is it constantly 
+ *   updating one image in-place?
+ *
+ * Different answers will favour different texture upload mechanisms.
+ * To upload an image that is purely outside of cache, a DMA-based
+ * upload will probably win, whereas for small, in-cache textures,
+ * copying looks good.
+ */
+#define NR_TEXOBJ 4
+static GLuint TexObj[NR_TEXOBJ];
+
+
 struct FormatRec {
    GLenum Format;
    GLenum Type;
@@ -121,32 +147,51 @@ TypeStr(GLenum type)
  * the driver, but it is better if the images are correctly aligned to
  * start with:
  */
-#define ALIGN (1<<7)
+#define ALIGN (1<<12)
+
+static unsigned align(unsigned value, unsigned a)
+{
+   return (value + a - 1) & ~(a-1);
+}
+
+static int MIN2(int a, int b)
+{
+   return a < b ? a : b;
+}
 
 static void
 MeasureDownloadRate(void)
 {
    const int w = TexWidth + 2 * TexBorder;
    const int h = TexHeight + 2 * TexBorder;
-   const int bytes = w * h * BytesPerTexel(Format);
+   const int image_bytes = align(w * h * BytesPerTexel(Format), ALIGN);
+   const int bytes = image_bytes * NR_TEXOBJ;
+   GLubyte *orig_texImage, *orig_getImage;
    GLubyte *texImage, *getImage;
    GLdouble t0, t1, time;
    int count;
    int i;
+   int offset = 0;
+   GLdouble total = 0;		/* ints will tend to overflow */
 
-   texImage = (GLubyte *) malloc(bytes + ALIGN);
-   getImage = (GLubyte *) malloc(bytes + ALIGN);
-   if (!texImage || !getImage) {
+   printf("allocating %d bytes for %d %dx%d images\n",
+	  bytes, NR_TEXOBJ, w, h);
+
+   orig_texImage = (GLubyte *) malloc(bytes + ALIGN);
+   orig_getImage = (GLubyte *) malloc(image_bytes + ALIGN);
+   if (!orig_texImage || !orig_getImage) {
       DownloadRate = 0.0;
       return;
    }
 
-   texImage = (GLubyte *)((((unsigned)texImage) + ALIGN) & ~(ALIGN-1));
-   getImage = (GLubyte *)((((unsigned)getImage) + ALIGN) & ~(ALIGN-1));
+   printf("alloc %p %p\n", orig_texImage, orig_getImage);
+
+   texImage = (GLubyte *)align((unsigned)orig_texImage, ALIGN);
+   getImage = (GLubyte *)align((unsigned)orig_getImage, ALIGN);   
 
    for (i = 1; !(((unsigned)texImage) & i); i<<=1)
       ;
-   printf("texture image alignment: %d bytes\n", i);
+   printf("texture image alignment: %d bytes (%p)\n", i, texImage);
       
    for (i = 0; i < bytes; i++) {
       texImage[i] = i & 0xff;
@@ -179,19 +224,57 @@ MeasureDownloadRate(void)
    count = 0;
    t0 = glutGet(GLUT_ELAPSED_TIME) * 0.001;
    do {
+      int img = count%NR_TEXOBJ;
+      GLubyte *img_ptr = texImage + img * image_bytes;
+
+      glBindTexture(GL_TEXTURE_2D, TexObj[img]);
+
       if (SubImage && count > 0) {
-         glTexSubImage2D(GL_TEXTURE_2D, 0, -TexBorder, -TexBorder, w, h,
+	 /* Only update a portion of the image each iteration.  This
+	  * is presumably why you'd want to use texsubimage, otherwise
+	  * you may as well just call teximage again.
+	  *
+	  * A bigger question is whether to use a pointer that moves
+	  * with each call, ie does the incoming data come from L2
+	  * cache under normal circumstances, or is it pulled from
+	  * uncached memory?  
+	  * 
+	  * There's a good argument to say L2 cache, ie you'd expect
+	  * the data to have been recently generated.  It's possible
+	  * that it could have come from a file read, which may or may
+	  * not have gone through the cpu.
+	  */
+         glTexSubImage2D(GL_TEXTURE_2D, 0, 
+			 -TexBorder, 
+			 -TexBorder + offset * h/8, 
+			 w, 
+			 h/8,
                          FormatTable[Format].Format,
-                         FormatTable[Format].Type, texImage);
+                         FormatTable[Format].Type, 
+#if 1
+			 texImage /* likely in L2$ */
+#else
+			 img_ptr + offset * bytes/8 /* unlikely in L2$ */
+#endif
+	    );
+	 offset += 1;
+	 offset %= 8;
+	 total += w * h / 8;
       }
       else {
          glTexImage2D(GL_TEXTURE_2D, 0,
                       FormatTable[Format].IntFormat, w, h, TexBorder,
                       FormatTable[Format].Format,
-                      FormatTable[Format].Type, texImage);
+                      FormatTable[Format].Type, 
+		      img_ptr);
+	 total += w*h;
       }
 
 #if 1
+      /* Render a texture, but not necessarily the one just uploaded.  
+       */
+/*       glBindTexture(GL_TEXTURE_2D, TexObj[(img + NR_TEXOBJ/2)%NR_TEXOBJ]); */
+
       /* draw a tiny polygon to force texture into texram */
       glBegin(GL_TRIANGLES);
       glTexCoord2f(0, 0);     glVertex2f(1, 1);
@@ -204,29 +287,17 @@ MeasureDownloadRate(void)
       t1 = glutGet(GLUT_ELAPSED_TIME) * 0.001;
       time = t1 - t0;
       count++;
+/*       printf("total %f count %d\n", total, count); */
    } while (time < 3.0);
 
    glDisable(GL_TEXTURE_2D);
 
-   printf("w*h=%d  count=%d  time=%f\n", w*h, count, time);
-   DownloadRate = w * h * count / time;
-
-#if 0
-   if (!ScaleAndBias) {
-      /* verify texture readback */
-      glGetTexImage(GL_TEXTURE_2D, 0,
-                    FormatTable[Format].Format,
-                    FormatTable[Format].Type, getImage);
-      for (i = 0; i < w * h; i++) {
-         if (texImage[i] != getImage[i]) {
-            printf("[%d] %d != %d\n", i, texImage[i], getImage[i]);
-         }
-      }
-   }
-#endif
+   printf("total texels=%f  time=%f\n", total, time);
+   DownloadRate = total / time;
+
 
-/*    free(texImage); */
-/*    free(getImage); */
+   free(orig_texImage); 
+   free(orig_getImage); 
 
    {
       GLint err = glGetError();