Re: [Ext2-devel] Re: [STUPID TESTCASE] ext3 htree vs. reiserfs on 2.5.40-mm1

Oleg Drokin
2002-10-07T06:49:18Z

Hello!

On Fri, Oct 04, 2002 at 11:09:35AM -0600, Andreas Dilger wrote:
> > > As a result, if the size of the directory + inode table blocks is larger
> > > than memory, and also larger than 1/4 of the journal, you are essentially
> > > seek-bound because of random block dirtying.
> > > You should see what the size of the directory is at its peak (probably
> > > 16 bytes * 300k ~= 5MB, and add in the size of the directory blocks
> > > (128 bytes * 300k ~= 38MB) and make the journal 4x as large as that,
> > > so 192MB (mke2fs -j -J size=192) and re-run the test (I assume you have
> > > at least 256MB+ of RAM on the test system).
> > Hm. But all of that won't help if you need to read inodes from disk first,
> > right? (until that inode allocation in chunks implemented, of course).
> Ah, but see the follow-up reply - increasing the size of the journal as
> advised improved the htree performance to 15% and 55% faster than
> reiserfs for creates and deletes, respectively:

Yes, but that was the case with warm caches, as I understand it.
Usually you cannot count that all inodes of large file set are already present
and should not be read.

> > > What is very interesting from the above results is that the CPU usage
> > > is _much_ smaller for ext3+htree than for reiserfs. It looks like
> > This is only in case of deletion, probably somehow related to constant item
> > shifting when some of the items are deleted.
> Well, even for creates it is 19% less CPU. The re-tested wall-clock

I afraid other parts of code might have contributed there.
Like setting s_dirt way more often than needed.

Bye,
Oleg