Re: Ext3 meta-data performance

[Andrew Morton <akpm@digeo.com>]

Nick Piggin <piggin@cyberone.com.au> wrote:
>
> >
>  >I have some more time to experiment, so please let me know if there is
>  >anything else you think I should try.
>  >
>  Andrew might be able to suggest some worthwhile tests, if nothing
>  else, try mounting your filesystems as ext2, so you can get a
>  baseline figure.

So the workload is a `cp -Rl' of a 500,000 file tree?

Vast amounts of metadata.  ext2 will fly through that.  Poor old ext3 has
to write everything twice, and has to keep on doing seek-intensive
checkpointing when the journal fills.

When we get Andreas's "dont bother reading empty inode blocks" speedup
going it will help both filesystems quite a bit.

Increasing the journal size _may_ help.  `tune2fs -J size=400', or `mke2fs
-j J size=400'.

The Orlov allocator will help this workload significantly, but you have to
give it time to settle in: it uses different decisions for the placement of
directories on disk.  If the source directory of the copy was created by a
2.4 filesystem then we won't get any of that benefit.