vk_pipeline_cache: build only the last two sessions' pipelines at boot

Each pipeline built at boot holds ~0.45 MB of driver memory. Mario Kart
World built 4,789 from the eight sessions the list kept, while one
session of its title screen uses ~1,500. With the last two sessions it
built 1,035 at boot and 972 when first needed: the emulator's own memory
at five minutes 6.4 -> 5.6 GB, frames over 100 ms 9 -> 10 (none built at
boot: 4.9 GB, but 38 frames over 100 ms). Lists saved with the longer
window are trimmed when they are loaded.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/video_core/renderer_vulkan/vk_pipeline_cache.cpp b/src/video_core/renderer_vulkan/vk_pipeline_cache.cpp
index e369caa58f..f877b9d341 100644
--- a/src/video_core/renderer_vulkan/vk_pipeline_cache.cpp
+++ b/src/video_core/renderer_vulkan/vk_pipeline_cache.cpp
@@ -563,7 +563,10 @@ namespace {
 // <title>/vulkan_used.bin: the graphics pipelines recent sessions used, as key hash + sessions
 // since the last use.
 constexpr u32 UsedPipelinesMagic = 0x31505545; // "EUP1"
-constexpr u8 UsedPipelinesMaxAge = 8;
+// Pipelines the last two sessions used are built at boot. Each holds ~0.45 MB of driver memory:
+// title 1 built 4,800 from eight sessions, 1.5 GB more than building them on first use (but that
+// stalled frames 4x as often), while one session of its title screen uses ~1,500.
+constexpr u8 UsedPipelinesMaxAge = 2;
 
 std::unordered_map<u64, u8> LoadUsedPipelines(const std::filesystem::path& path) {
     std::unordered_map<u64, u8> used;
@@ -581,7 +584,9 @@ std::unordered_map<u64, u8> LoadUsedPipelines(const std::filesystem::path& path)
             !file.read(reinterpret_cast<char*>(&age), sizeof(age))) {
             break;
         }
-        used.emplace(hash, age);
+        if (age < UsedPipelinesMaxAge) { // lists saved with a longer window
+            used.emplace(hash, age);
+        }
     }
     return used;
 }