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Date:      Fri, 28 Sep 2001 16:13:49 -0600
From:      Nate Williams <nate@yogotech.com>
To:        Kris Kennaway <kris@obsecurity.org>
Cc:        Nate Williams <nate@yogotech.com>, Alessandro de Manzano <ale@unixmania.net>, Sean Chittenden <sean@chittenden.org>, stable@FreeBSD.ORG
Subject:   Re: dirpref gives massive performance boost
Message-ID:  <15284.63005.31275.606644@nomad.yogotech.com>
In-Reply-To: <20010928151204.A16750@xor.obsecurity.org>
References:  <20010928141246.A15515@xor.obsecurity.org> <20010928232009.A29187@libero.sunshine.ale> <20010928142611.A15946@xor.obsecurity.org> <20010928143016.H29974@rand.tgd.net> <20010928233800.B29391@libero.sunshine.ale> <20010928144146.A16221@xor.obsecurity.org> <15284.62680.507872.259266@nomad.yogotech.com> <20010928151204.A16750@xor.obsecurity.org>

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> > > > > > Well, you need to wipe the disk so that when you restore it can lay
> > > > > > things out optimally from the start.
> > > > > 
> > > > > But turning on soft-updates should be sufficient to get these performance 
> > > > > boosts from this point on, correct?  -sc
> > > > 
> > > > AFAIK SU is not related to the physical layout of data on disk, this is
> > > > the work of UFS_DIRHASH.
> > > 
> > > No, that's something different.
> > > 
> > > # Directory hashing improves the speed of operations on very large
> > > # directories at the expense of some memory.
> > > # Warning: this is experimental code!
> > > options         UFS_DIRHASH
> > > 
> > > The changes to dirpref are an improved on-disk layout policy for
> > > directories (and files?)  It's enabled by default because there's no
> > > downside.
> > 
> > Again, I thought DIRHASH was an in-core data structure that helps with
> > cache lookups for large directories, and had no effect on the on-disk
> > layout.  (Hence the reason why it is 'safe' to use in -stable.)
> 
> Yes, like I said in the text you quoted, they *are* different things.

*DUH*  Yeah, I was confusing dirpref and DIRHASH.  My bad, sorry for the
braino....

My apologies Kris!



Nate

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