是否需要FileChannel.force和FileDescriptor.sync？ [英] Are FileChannel.force and FileDescriptor.sync both needed?

问题描述

在 https://stackoverflow.com/questions/730521/really-作者在写的答案摘要中写道：

In https://stackoverflow.com/questions/730521/really-force-file-sync-flush-in-java, the author writes in the summary of the answers:

使用c .force（true）后跟s.getFD（）。用于Java NIO的sync（）

Use c.force(true) followed by s.getFD().sync() for Java NIO

我的问题是：你真的需要吗？都？力不够吗？是不是强制和同步只是不同的接口做同样的事情？我无法找到确认这一点的任何地方。

My question is: do you really need both? Isn't force enough? Aren't force and sync just different interfaces for doing the same thing? I can't find anyplace where this is confirmed.

推荐答案

我的理解是正确答案是否。

My understanding is that the correct answer is No.

FileChannel .force调用 fdatasync 或 fsync 。这可以在OpenJDK源代码的jdk / src / solaris / native / sun / nio / ch / FileChannelImpl.c中看到。
FileDescriptor 调用fsync （为了找到这个更复杂。我最终将其追溯到jvm.cpp）。

FileChannel.force calls fdatasync or fsync. This can be seen in jdk/src/solaris/native/sun/nio/ch/FileChannelImpl.c on of the OpenJDK source code. FileDescriptor calls fsync (To find this out was more complex. I finally traced it to jvm.cpp).

我是链接问题的作者。所以我错了。什么是不够的是 FileOutputStream.flush。因为它是一个无操作。因此，您需要强制或同步。

I am the "author" of the linked question. So I was wrong. What is NOT enough is FileOutputStream.flush. because it is a no-op. You therefore either need force or sync.

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