Just look at it this way: Suppose the parameters of the disk say that
you can readahead 64k for "Free". Say I have a directory with 500
small files. (whatever the limit is, memory, bandwidth,
hitrate-chances: you need to put a limit on the readahead
somewhere....)
In the old situation that readahead would contain 64 files. So opening
a random other file will have a 10% chance of being in the cache, not
requiring another IO.
In the new situation, the 500 files would only occupy say 150k on the
disk. So the readahead hits 40% of the files, giving a 40% hitrate on
the next file.
The extra hitrate is for free (in terms of IO). That's what makes it
attractive.
Roger.
-- ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 ** *-- BitWizard writes Linux device drivers for any device you may have! --* ------ Microsoft SELLS you Windows, Linux GIVES you the whole house ------
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/