Correct and revise OpenGL texture pooling (#2709)

test/gl/resource_pool.test.cpp

@@ -0,0 +1,123 @@
+#if MLN_RENDER_BACKEND_OPENGL
+#include <mbgl/test/util.hpp>
+
+#include <unordered_set>
+
+#include <mbgl/gfx/backend_scope.hpp>
+#include <mbgl/gfx/types.hpp>
+#include <mbgl/gl/headless_backend.hpp>
+#include <mbgl/gl/context.hpp>
+
+using namespace mbgl;
+
+namespace {
+
+constexpr auto oneMB = 1024 * 1024;
+
+constexpr gl::Texture2DDesc makeDescOneMB() {
+    return {{1024, 1024}, gfx::TexturePixelType::Luminance, gfx::TextureChannelDataType::UnsignedByte};
+}
+
+} // namespace
+
+TEST(ResourcePool, TexturePool) {
+    gl::HeadlessBackend backend{{32, 32}};
+    gfx::BackendScope scope{backend};
+
+    gl::Context context{backend};
+    EXPECT_TRUE(context.empty(true));
+
+    auto& pool = context.getTexturePool();
+    EXPECT_LE(oneMB, pool.maxStorage());
+
+    EXPECT_EQ(pool.usedStorage(), 0);
+    EXPECT_EQ(pool.unusedStorage(), 0);
+    EXPECT_EQ(pool.storage(), 0);
+    EXPECT_FALSE(pool.isUsed(3));
+    EXPECT_FALSE(pool.isUnused(3));
+    EXPECT_FALSE(pool.isPooled(3));
+
+    auto id = pool.alloc(makeDescOneMB());
+    EXPECT_EQ(pool.usedStorage(), oneMB);
+    EXPECT_EQ(pool.unusedStorage(), 0);
+    EXPECT_EQ(pool.storage(), oneMB);
+    EXPECT_TRUE(pool.isUsed(id));
+    EXPECT_FALSE(pool.isUnused(id));
+    EXPECT_TRUE(pool.isPooled(id));
+
+    pool.release(id);
+    EXPECT_EQ(pool.usedStorage(), 0u);
+    EXPECT_EQ(pool.unusedStorage(), oneMB);
+    EXPECT_EQ(pool.storage(), oneMB);
+    EXPECT_FALSE(pool.isUsed(id));
+    EXPECT_TRUE(pool.isUnused(id));
+    EXPECT_TRUE(pool.isPooled(id));
+
+    auto reused_id = pool.alloc(makeDescOneMB());
+    EXPECT_EQ(reused_id, id);
+    EXPECT_EQ(pool.usedStorage(), oneMB);
+    EXPECT_EQ(pool.unusedStorage(), 0);
+    EXPECT_EQ(pool.storage(), oneMB);
+    EXPECT_TRUE(pool.isUsed(id));
+    EXPECT_FALSE(pool.isUnused(id));
+    EXPECT_TRUE(pool.isPooled(id));
+
+    std::unordered_set<gl::TextureID> ids = {id};
+    while (pool.storage() <= pool.maxStorage()) {
+        auto new_id = pool.alloc(makeDescOneMB());
+        EXPECT_TRUE(ids.find(new_id) == ids.end());
+        ids.insert(new_id);
+        EXPECT_EQ(pool.usedStorage(), oneMB * ids.size());
+        EXPECT_EQ(pool.unusedStorage(), 0);
+        EXPECT_EQ(pool.storage(), pool.usedStorage());
+        EXPECT_TRUE(pool.isUsed(new_id));
+        EXPECT_FALSE(pool.isUnused(new_id));
+        EXPECT_TRUE(pool.isPooled(new_id));
+    }
+
+    EXPECT_LE(pool.maxStorage(), pool.usedStorage());
+    EXPECT_EQ(pool.usedStorage(), oneMB * ids.size());
+    EXPECT_EQ(pool.unusedStorage(), 0);
+    EXPECT_EQ(pool.storage(), pool.usedStorage());
+    EXPECT_TRUE(pool.isUsed(id));
+    EXPECT_FALSE(pool.isUnused(id));
+    EXPECT_TRUE(pool.isPooled(id));
+
+    pool.release(id);
+    ids.erase(id);
+    EXPECT_GE(pool.maxStorage(), pool.usedStorage());
+    EXPECT_EQ(pool.usedStorage(), oneMB * ids.size());
+    EXPECT_EQ(pool.unusedStorage(), 0);
+    EXPECT_EQ(pool.storage(), pool.usedStorage());
+    EXPECT_FALSE(pool.isUsed(id));
+    EXPECT_FALSE(pool.isUnused(id));
+    EXPECT_FALSE(pool.isPooled(id));
+
+    size_t used = pool.usedStorage();
+    size_t unused = 0;
+    while (!ids.empty()) {
+        auto i = *ids.begin();
+        pool.release(i);
+        ids.erase(i);
+        used -= oneMB;
+        unused += oneMB;
+        EXPECT_EQ(pool.usedStorage(), used);
+        EXPECT_EQ(pool.unusedStorage(), unused);
+        EXPECT_EQ(pool.storage(), used + unused);
+        EXPECT_FALSE(pool.isUsed(i));
+        EXPECT_TRUE(pool.isUnused(i));
+        EXPECT_TRUE(pool.isPooled(i));
+    }
+
+    context.reduceMemoryUsage();
+    context.renderingStats().numActiveTextures = 0;
+    EXPECT_EQ(pool.usedStorage(), 0);
+    EXPECT_EQ(pool.unusedStorage(), 0);
+    EXPECT_EQ(pool.storage(), 0);
+    EXPECT_FALSE(pool.isUsed(id));
+    EXPECT_FALSE(pool.isUnused(id));
+    EXPECT_FALSE(pool.isPooled(id));
+    EXPECT_TRUE(context.empty(true));
+}
+
+#endif