Re: [Ext2-devel] Re: Shrinking ext3 directories

Bill Davidsen
2002-06-20T16:30:58Z

On Thu, 20 Jun 2002, Andreas Dilger wrote:

> Remember also that each leaf block merge will incur a copy from the tail
> block (which may need to be read from disk) and then a truncate to drop
> that block. We _could_ leave some number of empty dir blocks at the end
> of the directory file if we had some sort of dir prealloc scheme happening.
> There would be some amount of hysteresis there to avoid the repeated
> alloc/free overhead (i.e. keep no more than 8 free blocks, but allocate
> 8 blocks at a time if you need more).

Wouldn't the hysteresis be the frag or block size? Is there benefit to
truncating if it doesn't free any disk space? Actually, there might be
benefit to leaving a few empty blocks at the end of the dir when doing
trunc as a means of reducing alloc.

--
bill davidsen <davidsen@tmr.com>
CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.