#include "st_context.h"
#include "st_cb_bitmap.h"
#include "st_cb_readpixels.h"
+#include "st_debug.h"
#include "state_tracker/st_cb_texture.h"
#include "state_tracker/st_format.h"
#include "state_tracker/st_pbo.h"
#include "state_tracker/st_texture.h"
+/* The readpixels cache caches a blitted staging texture so that back-to-back
+ * calls to glReadPixels with user pointers require less CPU-GPU synchronization.
+ *
+ * Assumptions:
+ *
+ * (1) Blits have high synchronization overheads, and it is beneficial to
+ * use a single blit of the entire framebuffer instead of many smaller
+ * blits (because the smaller blits cannot be batched, and we have to wait
+ * for the GPU after each one).
+ *
+ * (2) transfer_map implicitly involves a blit as well (for de-tiling, copy
+ * from VRAM, etc.), so that it is beneficial to replace the
+ * _mesa_readpixels path as well when possible.
+ *
+ * Change this #define to true to fill and use the cache whenever possible
+ * (this is inefficient and only meant for testing / debugging).
+ */
+#define ALWAYS_READPIXELS_CACHE false
+
static boolean
needs_integer_signed_unsigned_conversion(const struct gl_context *ctx,
GLenum format, GLenum type)
return dst;
}
+static struct pipe_resource *
+try_cached_readpixels(struct st_context *st, struct st_renderbuffer *strb,
+ bool invert_y,
+ GLsizei width, GLsizei height,
+ GLenum format,
+ enum pipe_format src_format, enum pipe_format dst_format)
+{
+ struct pipe_resource *src = strb->texture;
+ struct pipe_resource *dst = NULL;
+
+ if (ST_DEBUG & DEBUG_NOREADPIXCACHE)
+ return NULL;
+
+ /* Reset cache after invalidation or switch of parameters. */
+ if (st->readpix_cache.src != src ||
+ st->readpix_cache.dst_format != dst_format ||
+ st->readpix_cache.level != strb->surface->u.tex.level ||
+ st->readpix_cache.layer != strb->surface->u.tex.first_layer) {
+ pipe_resource_reference(&st->readpix_cache.src, src);
+ pipe_resource_reference(&st->readpix_cache.cache, NULL);
+ st->readpix_cache.dst_format = dst_format;
+ st->readpix_cache.level = strb->surface->u.tex.level;
+ st->readpix_cache.layer = strb->surface->u.tex.first_layer;
+ st->readpix_cache.hits = 0;
+ }
+
+ /* Decide whether to trigger the cache. */
+ if (!st->readpix_cache.cache) {
+ if (!strb->use_readpix_cache && !ALWAYS_READPIXELS_CACHE) {
+ /* Heuristic: If previous successive calls read at least a fraction
+ * of the surface _and_ we read again, trigger the cache.
+ */
+ unsigned threshold = MAX2(1, strb->Base.Width * strb->Base.Height / 8);
+
+ if (st->readpix_cache.hits < threshold) {
+ st->readpix_cache.hits += width * height;
+ return NULL;
+ }
+
+ strb->use_readpix_cache = true;
+ }
+
+ /* Fill the cache */
+ st->readpix_cache.cache = blit_to_staging(st, strb, invert_y,
+ 0, 0,
+ strb->Base.Width,
+ strb->Base.Height, format,
+ src_format, dst_format);
+ }
+
+ /* Return an owning reference to stay consistent with the non-cached path */
+ pipe_resource_reference(&dst, st->readpix_cache.cache);
+
+ return dst;
+}
+
/**
* This uses a blit to copy the read buffer to a texture format which matches
* the format and type combo and then a fast read-back is done using memcpy.
unsigned bind = PIPE_BIND_TRANSFER_READ;
struct pipe_transfer *tex_xfer;
ubyte *map = NULL;
+ bool window;
/* Validate state (to be sure we have up-to-date framebuffer surfaces)
* and flush the bitmap cache prior to reading. */
return;
}
- /* See if the texture format already matches the format and type,
- * in which case the memcpy-based fast path will likely be used and
- * we don't have to blit. */
- if (_mesa_format_matches_format_and_type(rb->Format, format,
- type, pack->SwapBytes, NULL)) {
- goto fallback;
- }
-
if (needs_integer_signed_unsigned_conversion(ctx, format, type)) {
goto fallback;
}
- dst = blit_to_staging(st, strb,
- st_fb_orientation(ctx->ReadBuffer) == Y_0_TOP,
- x, y, width, height, format,
- src_format, dst_format);
- if (!dst)
- goto fallback;
+ /* Cache a staging texture for back-to-back ReadPixels, to avoid CPU-GPU
+ * synchronization overhead.
+ */
+ dst = try_cached_readpixels(st, strb,
+ st_fb_orientation(ctx->ReadBuffer) == Y_0_TOP,
+ width, height, format, src_format, dst_format);
+ if (dst) {
+ window = false;
+ } else {
+ /* See if the texture format already matches the format and type,
+ * in which case the memcpy-based fast path will likely be used and
+ * we don't have to blit. */
+ if (_mesa_format_matches_format_and_type(rb->Format, format,
+ type, pack->SwapBytes, NULL)) {
+ goto fallback;
+ }
+
+ dst = blit_to_staging(st, strb,
+ st_fb_orientation(ctx->ReadBuffer) == Y_0_TOP,
+ x, y, width, height, format,
+ src_format, dst_format);
+ if (!dst)
+ goto fallback;
+
+ window = true;
+ }
/* map resources */
pixels = _mesa_map_pbo_dest(ctx, pack, pixels);
goto fallback;
}
+ if (!window)
+ map += y * tex_xfer->stride + x * util_format_get_blocksize(dst_format);
+
/* memcpy data into a user buffer */
{
const uint bytesPerRow = width * util_format_get_blocksize(dst_format);
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