Re: [PATCHES] TODO Item - Add system view to show free space map

On Fri, Oct 28, 2005 at 05:05:25PM +0100, Simon Riggs wrote:
> 3. Helping Readahead efficiency: Currently blocks are allocated one at a
> time. If many tables are extending at the same time, the blocks from
> multiple tables will be intermixed together on the disk. Reading the
> data back takes more head movement and reduces the I/O rate. Allocating

Ok, I agree with the rest but this isn't true. Any filesystem designed
in the last ten years leaves gaps around the place so when you extend a
file it remains consecutive. Some filesystems (like XFS) take it to
extremes). Interleaving blocks with this pattern hasn't been done since
FAT.

That isn't to say that preextending isn't a good idea. With my pread()
patch it was the one use of lseek() I couldn't remove.

Other than that, good thought...

Have a nice dat,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.