在 Java 中，当调用 AsynchronousFileChannel.write(...) 时，会收到一个 Future，然后可以通过 Future 等待完成。 get().
当 get() 调用返回时，写入是否已写入磁盘或仅写入页面缓存？
如果重要的话，我很好奇的具体平台是 Linux 和 ext4。
最佳答案
查看此文档:
看起来即使在 get 方法在 Future 上返回后，操作系统级别的一些缓存可能会阻止内容写入磁盘。如果您想真正确定，我认为您必须在 Future 返回后执行 force。
相关摘录:
Forces any updates to this channel's file to be written to the storage device that contains it. If this channel's file resides on a local storage device then when this method returns it is guaranteed that all changes made to the file since this channel was created, or since this method was last invoked, will have been written to that device. This is useful for ensuring that critical information is not lost in the event of a system crash.
If the file does not reside on a local device then no such guarantee is made.
The metaData parameter can be used to limit the number of I/O operations that this method is required to perform. Passing false for this parameter indicates that only updates to the file's content need be written to storage; passing true indicates that updates to both the file's content and metadata must be written, which generally requires at least one more I/O operation. Whether this parameter actually has any effect is dependent upon the underlying operating system and is therefore unspecified.
Invoking this method may cause an I/O operation to occur even if the channel was only opened for reading. Some operating systems, for example, maintain a last-access time as part of a file's metadata, and this time is updated whenever the file is read. Whether or not this is actually done is system-dependent and is therefore unspecified.
This method is only guaranteed to force changes that were made to this channel's file via the methods defined in this class.
关于java - AsynchronousFileChannel 何时写入 "complete"？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33205703/
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