Optimize the efficiency of DualKeyCacheImpl's mayEvict (apache#16445)

Author: luoluoyuyu

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/conf/IoTDBConfig.java

@@ -980,6 +980,12 @@ public class IoTDBConfig {
   /** Policy of DataNodeSchemaCache eviction */
   private String dataNodeSchemaCacheEvictionPolicy = "FIFO";
 
+  /**
+   * Threshold for cache size in mayEvict. When cache size exceeds this threshold, the system will
+   * compute total memory in each eviction iteration to ensure accurate memory management.
+   */
+  private int cacheEvictionMemoryComputationThreshold = 20;
+
   private int dataNodeTableCacheSemaphorePermitNum = 5;
 
   /** GRASS Service */
@@ -3269,6 +3275,15 @@ public void setDataNodeSchemaCacheEvictionPolicy(String dataNodeSchemaCacheEvict
     this.dataNodeSchemaCacheEvictionPolicy = dataNodeSchemaCacheEvictionPolicy;
   }
 
+  public int getCacheEvictionMemoryComputationThreshold() {
+    return cacheEvictionMemoryComputationThreshold;
+  }
+
+  public void setCacheEvictionMemoryComputationThreshold(
+      int cacheEvictionMemoryComputationThreshold) {
+    this.cacheEvictionMemoryComputationThreshold = cacheEvictionMemoryComputationThreshold;
+  }
+
   public int getDataNodeTableCacheSemaphorePermitNum() {
     return dataNodeTableCacheSemaphorePermitNum;
   }

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/conf/IoTDBDescriptor.java

@@ -1061,6 +1061,12 @@ public void loadProperties(TrimProperties properties) throws BadNodeUrlException
         properties.getProperty(
             "datanode_schema_cache_eviction_policy", conf.getDataNodeSchemaCacheEvictionPolicy()));
 
+    conf.setCacheEvictionMemoryComputationThreshold(
+        Integer.parseInt(
+            properties.getProperty(
+                "cache_eviction_memory_computation_threshold",
+                String.valueOf(conf.getCacheEvictionMemoryComputationThreshold()))));
+
     conf.setDataNodeTableCacheSemaphorePermitNum(
         Integer.parseInt(
             properties.getProperty(
@@ -2131,6 +2137,13 @@ public synchronized void loadHotModifiedProps(TrimProperties properties)
       // update trusted_uri_pattern
       loadTrustedUriPattern(properties);
 
+      // update cache_eviction_memory_computation_threshold
+      conf.setCacheEvictionMemoryComputationThreshold(
+          Integer.parseInt(
+              properties.getProperty(
+                  "cache_eviction_memory_computation_threshold",
+                  String.valueOf(conf.getCacheEvictionMemoryComputationThreshold()))));
+
       // tvlist_sort_threshold
       conf.setTVListSortThreshold(
           Integer.parseInt(

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/analyze/cache/schema/dualkeycache/impl/DualKeyCacheImpl.java

@@ -19,6 +19,7 @@
 
 package org.apache.iotdb.db.queryengine.plan.analyze.cache.schema.dualkeycache.impl;
 
+import org.apache.iotdb.db.conf.IoTDBDescriptor;
 import org.apache.iotdb.db.queryengine.plan.analyze.cache.schema.dualkeycache.IDualKeyCache;
 import org.apache.iotdb.db.queryengine.plan.analyze.cache.schema.dualkeycache.IDualKeyCacheStats;
 
@@ -199,12 +200,13 @@ public void update(
 
   private void mayEvict() {
     long exceedMemory;
+    final int threshold =
+        IoTDBDescriptor.getInstance().getConfig().getCacheEvictionMemoryComputationThreshold();
     while ((exceedMemory = cacheStats.getExceedMemory()) > 0) {
       // Not compute each time to save time when FK is too many
-      // The hard-coded size is 100
       do {
         exceedMemory -= evictOneCacheEntry();
-      } while (exceedMemory > 0 && firstKeyMap.size() > 100);
+      } while (exceedMemory > 0 && firstKeyMap.size() > threshold);
     }
   }