YQL-18327 Disable yellow zone of allocator on 50%. Update yellow zone on free (#4298)

Author: lll-phill-lll

ydb/library/yql/minikql/aligned_page_pool.cpp

@@ -379,6 +379,7 @@ void TAlignedPagePoolImpl<T>::ReturnBlock(void* ptr, size_t size) noexcept {
         Y_DEBUG_ABORT_UNLESS(ActiveBlocks.erase(ptr));
     }
 #endif
+    UpdateMemoryYellowZone();
 }
 
 template<typename T>
@@ -500,6 +501,19 @@ void TAlignedPagePoolImpl<T>::Free(void* ptr, size_t size) noexcept {
     }
 }
 
+template<typename T>
+void TAlignedPagePoolImpl<T>::UpdateMemoryYellowZone() {
+    if (IncreaseMemoryLimitCallback) return;
+    if (Limit == 0) return;
+
+    ui8 usedMemoryPercent = 100 * GetUsed() / Limit;
+    if (usedMemoryPercent >= EnableMemoryYellowZoneThreshold) {
+        IsMemoryYellowZoneReached = true;
+    } else if (usedMemoryPercent <= DisableMemoryYellowZoneThreshold) {
+        IsMemoryYellowZoneReached = false;
+    }
+}
+
 template<typename T>
 bool TAlignedPagePoolImpl<T>::TryIncreaseLimit(ui64 required) {
     if (!IncreaseMemoryLimitCallback) {

ydb/library/yql/minikql/aligned_page_pool.h

@@ -237,13 +237,7 @@ class TAlignedPagePoolImpl {
         UpdateMemoryYellowZone();
     }
 
-    void UpdateMemoryYellowZone() {
-        if (IncreaseMemoryLimitCallback) return;
-
-        if (Limit != 0) {
-            IsMemoryYellowZoneReached = (100 * GetUsed() / Limit) > MemoryYellowZoneThreshold;
-        }
-    }
+    void UpdateMemoryYellowZone();
 
     bool TryIncreaseLimit(ui64 required);
 
@@ -279,8 +273,10 @@ class TAlignedPagePoolImpl {
     // Indicates when memory limit is almost reached.
     bool IsMemoryYellowZoneReached = false;
     // This theshold is used to determine is memory limit is almost reached.
-    // If TIncreaseMemoryLimitCallback is set this threshold should be ignored.
-    const ui8 MemoryYellowZoneThreshold = 80;
+    // If TIncreaseMemoryLimitCallback is set this thresholds should be ignored.
+    // The yellow zone turns on when memory consumption reaches 80% and turns off when consumption drops below 50%.
+    const ui8 EnableMemoryYellowZoneThreshold = 80;
+    const ui8 DisableMemoryYellowZoneThreshold = 50;
 };
 
 using TAlignedPagePool = TAlignedPagePoolImpl<>;

ydb/library/yql/minikql/aligned_page_pool_ut.cpp

@@ -131,6 +131,49 @@ Y_UNIT_TEST(UnalignedMmapUnalignedSize) {
     );
 }
 
+Y_UNIT_TEST(YellowZoneSwitchesCorrectlyBlock) {
+    TAlignedPagePool::ResetGlobalsUT();
+    TAlignedPagePoolImpl alloc(__LOCATION__);
+
+    // choose relatively big chunk so ALLOC_AHEAD_PAGES don't affect the correctness of the test 
+    auto size = 1024 * TAlignedPagePool::POOL_PAGE_SIZE;
+
+    alloc.SetLimit(size * 10);
+
+    // 50% allocated -> no yellow zone
+    auto block1 = alloc.GetBlock(size * 5);
+    UNIT_ASSERT_VALUES_EQUAL(false, alloc.IsMemoryYellowZoneEnabled());
+
+    // 70% allocated -> no yellow zone
+    auto block2 = alloc.GetBlock(size * 2);
+    UNIT_ASSERT_VALUES_EQUAL(false, alloc.IsMemoryYellowZoneEnabled());
+
+    // 90% allocated -> yellow zone is enabled (> 80%)
+    auto block3 = alloc.GetBlock(size * 2);
+    UNIT_ASSERT_VALUES_EQUAL(true, alloc.IsMemoryYellowZoneEnabled());
+
+    // 70% allocated -> yellow zone is still enabled (> 50%)
+    alloc.ReturnBlock(block3, size * 2);
+    UNIT_ASSERT_VALUES_EQUAL(true, alloc.IsMemoryYellowZoneEnabled());
+
+    // 50% allocated -> yellow zone is disabled
+    alloc.ReturnBlock(block2, size * 2);
+    UNIT_ASSERT_VALUES_EQUAL(false, alloc.IsMemoryYellowZoneEnabled());
+
+    // 0% allocated -> yellow zone is disabled
+    alloc.ReturnBlock(block1, size * 5);
+    UNIT_ASSERT_VALUES_EQUAL(false, alloc.IsMemoryYellowZoneEnabled());
+}
+
+Y_UNIT_TEST(YellowZoneZeroDivision) {
+    TAlignedPagePool::ResetGlobalsUT();
+    TAlignedPagePoolImpl alloc(__LOCATION__);
+
+    alloc.SetLimit(0);
+
+    UNIT_ASSERT_EQUAL(false, alloc.IsMemoryYellowZoneEnabled());
+}
+
 } // Y_UNIT_TEST_SUITE(TAlignedPagePoolTest)
 
 } // namespace NMiniKQL