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SubjectRe: Filesystem optimization..
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>When doing a path lookup, the directory must already have been
>read. Embedding the inode has the neat advantage that reading the
>directory automatically pulls the inode in at a very low cost.

Maybe, maybe not. If the directory entry you seek is not at
the beginning of the directory, you may have to read more directory
blocks from disk (proportional to the increased size of the enhanced
directory entry) to reach the one you want.

If the enhanced directory blocks are cached and the
pre-enhancement inode blocks wouldn't have been cached... that's
probably a reasonable I/O improvement. If the enhanced directory
blocks are not cached, and are not allocated consecutively and
read-ahead... this could be a performance penalty.

What it boils down to, I think, is that someone needs to
implement this idea so it can be tested in real systems. The result
of the tests will determine whether the time spend implementing it was
worthwhile. :-)

Craig Milo Rogers


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