zongtanghu opened a new issue #522: org.apache.rocketmq.store.MappedFile#warmMappedFile() method has some Ineffective code and result double io in the sync flush URL: https://github.com/apache/rocketmq/issues/522 1.What is the purpose of the change? In the part of RocketMQ store,the goal of the warm-up mappedFile is that prewrite some random value into memory page corresponding to the mappedFile,so the target memory will swap to the physical memory in advance.But in fact,this action will result in double IO to the operation system.First IO is in the warm-up MappedFile,and secode IO is in the process of write message data into pagecache. 2.Optimization change action Because of the above reason,we can remove the part of write some random value,prevent-gc and force flush codes in the warm-up method.In the mmapOperation,we can call mlock() method directly.
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