Messages in this thread | | | Date | Tue, 17 Aug 2010 20:29:20 +0200 | From | Andi Kleen <> | Subject | Re: Proposal: Use hi-res clock for file timestamps |
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> OK, so that leaves us with the race, even on newer filesystems: > > 1. File is modified, mtime updated > 2. Client fetches mtime to revalidate cache > 3. File is modified again, mtime updated > 4. Client fetches new mtime to revalidate cache
You'll always have a race window with time, the only way around that would be a version number. > - Tell everyone to use NFSv4 (and make sure we have > changeattr/i_version working correctly). > - Use a finer-grained time source. (I believe you when you say > the TSC is too slow, but maybe we should run some tests to > make sure.)
It depends on the CPU too.
> - Increment mtime by a nanosecond when necessary.
You cannot be more precise than the backing file system: this causes non monotonity when the inodes are flushed (has happened in the past)
-Andi
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