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Posted to dev@rocketmq.apache.org by GitBox <gi...@apache.org> on 2022/08/17 02:28:06 UTC

[GitHub] [rocketmq] maoyiyong-svg opened a new issue, #4829: RocketMq内存映射文件的具体实现MappedFile中关于方法commit0()中往channel中写数据的优化。

maoyiyong-svg opened a new issue, #4829:
URL: https://github.com/apache/rocketmq/issues/4829

   在org.apache.rocketmq.store.MappedFile#commit0中使用“this.fileChannel.write(byteBuffer);”导致没有利用文件内存映射机制，导致写入效率降低。
   原因：
   在MappedFile对象实例化的时候就会实例化fileChannel和MappedByteBuffer，完成之后在finally中可以直接关闭fileChannel，之后的数据读写应该使用MappedByteBuffer，通过文件内存映射来操作。
   ![image](https://user-images.githubusercontent.com/62745186/185017246-044241e1-5703-434b-a8e8-5946d66af6ae.png)
   此处建议使用mappedByteBuffer进行数据写入。
   ![image](https://user-images.githubusercontent.com/62745186/185020982-007dbe10-ad61-45e3-99e7-670b93aef5e4.png)
   


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[GitHub] [rocketmq] RongtongJin commented on issue #4829: Suggestion of commit0 method in MappedFile

Posted by GitBox <gi...@apache.org>.
RongtongJin commented on issue #4829:
URL: https://github.com/apache/rocketmq/issues/4829#issuecomment-1217520381

   @maoyiyong-svg 你好，MappedFile commit方法是在transientStorePoolEnable开启后使用的，其作用时将消息数据从RocketMQ自己管理的堆外内存写入到文件中（后面再由flush线程刷到磁盘），所以代码中出现了writeBuffer中的数据写到fileChannel中，实际上当开启transientStorePoolEnable后，写消息数据都是先写入到writeBuffer而非到内存映射的mappedByteBuffer（若不开启transientStorePoolEnable则是直接写到内存映射文件中）。


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[GitHub] [rocketmq] maoyiyong-svg closed issue #4829: Suggestion of commit0 method in MappedFile

Posted by GitBox <gi...@apache.org>.
maoyiyong-svg closed issue #4829: Suggestion of commit0 method in MappedFile
URL: https://github.com/apache/rocketmq/issues/4829


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