Andreas Dilger <adil...@dilger.ca> wrote:
> Given that calling SEEK_HOLE is also going to have some cost, my suggestion
> would be to ignore st_blocks completely for small files (size < 64KB) and
> just read the file in this case, since the overhead of reading will probably
> be about the same as checking if any blocks are allocated. If no blocks are
> allocated, then the read will not do any disk IO, and if there are blocks
> allocated they would have needed to be read from disk anyway and SEEK_HOLE
> would be pure overhead.
If you propose to ignore st_blocks completely for small files that are on
historic (unmaintained) filesystems without SEEK_HOLE support, this is what
star does since years ;-)
> To catch larger files that have been written to cache but haven't flushed
> data to disk yet, it might still make sense to use SEEK_HOLE on larger files
> with st_blocks == 0, especially if they have a recent mtime.
Using mtime does not look like a good idea in this context.
Jörg
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