Re: structure dentry help...

Jamie Lokier (lkd@tantalophile.demon.co.uk)
Tue, 2 Nov 1999 13:24:16 +0100


Alexander Viro wrote:
> c) we have only two states for dentry - hashed and unhashed.
> Life would be much easier if we had finer separation (e.g. special case
> for dentry in process of lookup()). To be changed.

Directory lookups following readdir(), and quite possibly following
other lookups, would be faster if filesystems had the option of creating
"dentry without inode", such that lookup would do iget() on them.

It only makes sense for filesystems where readdir() produces a key that
it useful for a subsequent iget().

I know there was some work on caching the pointer within a directory for
lookup, and that B-trees will arrive for ext2 eventually. But neither
of those can get the same performance as caching inode numbers, when
seek times dominate inode read performance.

-- Jamie

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