ASTC: decode and re-compress to BC1/BC3 on the GPU; texture cache budget

- accelerate_astc=Gpu with astc_recompression=Bc1/Bc3 now decodes ASTC
  with the GPU decoder into a temporary RGBA8 image (dedicated memory,
  freed once the GPU is past it) and compresses it with a new compute
  shader (bc_encoder.comp: bounding-box endpoints along the colours'
  covariance, inset 1/16, nearest palette entry; BC3 alpha ramp; BC1
  punch-through), then copies the blocks into the image. No CPU decode,
  so streamed textures are ready the frame they are first used instead
  of showing placeholders for seconds; the decode pass no longer waits
  for the GPU on this path.
- The CPU path (CpuAsynchronous) fills a new image with zero blocks
  before its first decode instead of showing stale VRAM, and the
  transcode pool is a quarter of the hardware threads.
- Switch 2 titles: collector thresholds near the device budget, re-read
  every 60 frames from VK_EXT_memory_budget (another game shrank it from
  7.0 to 5.4 GB).
- EDEN_NX2_HIDE_WINDOW=0 now leaves the window visible.

1 files changed, 5 insertions, 4 deletions

diff --git a/src/video_core/textures/workers.cpp b/src/video_core/textures/workers.cpp
index 6922634e30..e3a0f26cf2 100644
--- a/src/video_core/textures/workers.cpp
+++ b/src/video_core/textures/workers.cpp
@@ -11,14 +11,15 @@
 namespace Tegra::Texture {
 
 Common::ThreadWorker& GetThreadWorkers() {
-    // An eighth of the hardware threads (at least 2): with half, re-compressing streamed ASTC
-    // textures took ~3.5 cores from the emulated CPU cores and the GPU thread on an 8-core
-    // laptop. EDEN_NX2_TRANSCODE_THREADS=<n> overrides.
+    // A quarter of the hardware threads (at least 2). Half took ~3.5 cores from the emulated
+    // CPU cores and the GPU thread on an 8-core laptop when textures were thrashing; with an
+    // eighth (2) both threads stayed saturated and streamed textures arrived seconds late (shown
+    // as placeholders), while 4 cost no frame rate. EDEN_NX2_TRANSCODE_THREADS=<n> overrides.
     static Common::ThreadWorker workers{[] {
         if (const char* text = std::getenv("EDEN_NX2_TRANSCODE_THREADS")) {
             return (std::max)(static_cast<u32>(std::strtoul(text, nullptr, 10)), 1U);
         }
-        return (std::max)(std::thread::hardware_concurrency() / 8, 2U);
+        return (std::max)(std::thread::hardware_concurrency() / 4, 2U);
     }(), "ImageTranscode"};
     return workers;
 }