cache attribute and chunks for open files #528
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SandyXSD
reviewed
Jun 18, 2021
| o.files[ino] = of | ||
| } else if attr != nil && attr.Mtime == of.attr.Mtime && attr.Mtimensec == of.attr.Mtimensec { | ||
| attr.KeepCache = true | ||
| } else { |
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This is the only place to assign KeepCache (initialized as zero).
| defer o.Unlock() | ||
| of, ok := o.files[ino] | ||
| if ok && time.Since(of.lastCheck) < o.expire { | ||
| *attr = of.attr |
SandyXSD
approved these changes
Jun 18, 2021
|
May I ask, if I only use juicefs on linux, is it possible to do same thing without the openfile.go? I just need to mount filesystem without setting ExplicitDataCacheControl of MountOptions and always set FOPEN_KEEP_CACHE when I open a file, because linux kernel can invalidates the page cache by detecting the length or the modification time of the file has changed. |
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For not-modified files, we should keep the page cache in kernel, also cache the chunks to speed up read.
For any changes to the data, the mtime of file will be updated in microseconds, so we can check the mtime to know whether the file is changed or not. If not, we will keep the cache for chunks and pages in kernel, otherwise invalidate them.
And, we introduce a new option called
OpenCache, which tell the client to don't check the mtime of a file before that, then JuiceFS will not know any change in the past period. SoOpenCacheshould be set based on the change interval of files.TODO: add command option for OpenCache
Closes #454