On Wed, Apr 26 2006, Linus Torvalds wrote:
> It would be interesting to see where doing gang-lookup moves the target, 
> but on the other hand, with smaller files (and small files are still 
> common), gang lookup isn't going to help as much.

Here is the graph for:

- 2.6.17-rc3 + splice reada fix (vanilla-no-gang)

vs

- 2.6.17-rc3 + splice reada fix + gang lookup (vanilla)

vs

- 2.6.17-rc3 + splice reada fix + lockless page cache (lockless-no-gang)

Average of 3 runs graphed, the lockless run didn't use the batch lookup
as that is a lot slower since it basically defeats the purpose of the
lockless page cache until Nick patches it up :-)

Conclusion: the gang lookup makes things faster for the vanilla kernel,
but it only makes it scale marginally (if at all) better.

-- 
Jens Axboe