How to reduce size of STAT_AsyncFileMemory

Hi,when my iPhoneX loaded steaming levels and I print memory usage by ‘memreport -full’:

LogMemory: 392232960 - PakCache High Water - STAT_PakCacheHighWater - STATGROUP_Memory - STATCAT_Advanced

LogMemory: 13238272 - PakCache Current - STAT_PakCacheMem - STATGROUP_Memory - STATCAT_Advanced

LogMemory: 959992938 - Async File Handle Memory - STAT_AsyncFileMemory - STATGROUP_Memory - STATCAT_Advanced

why STAT_AsyncFileMemory is so high, and how to reduce size?