Re: Ext3 meta-data performance

From: Andrew Morton (akpm@digeo.com)
Date: Fri May 30 2003 - 11:24:28 EST


Nick Piggin <piggin@xxxxxxxxxxxxxxx> 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.


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