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Re: [RFC] FSFS filesystem options (long, sorry)

From: Michael Sinz <Michael.Sinz_at_sinz.org>
Date: 2007-03-05 16:17:09 CET

On 3/5/07, Mattias Engdegård <mattias@virtutech.se> wrote:
> "Michael Sinz" <Michael.Sinz@sinz.org> writes:
> >(It is not like we are saving any storage space by not having it
> >complete, even when/if we start talking about 650,000 revisions -
> >that is only 6 characters of filename and even if stored in 32-bit
> >unicode, that comes to 24 bytes within the inode or directory entry.
> >(Unless we want to work on old PDP-11/RT-11 systems with 6.3
> >character file names and over 1 million revisions :-)
> It's not a matter of storage space but performance. Shorter names means
> that more of them fit into a directory block on disk, more of them fit
> into
> cache, and more of them are returned with each getdents() system call.

That would be true for which filesystems? (That is, with names this short)
Many of them optimize space usage granular chunks to keep things on
32-bit and/or 64-bit boundaries at a minimum - if not full cache-line sizes.

(Strangely aligned data structures are much slower than a slight loss in
data density - especially at the byte and word level due to the need to
execute mixed or multiple bus cycles to collect the various parts.)

Michael Sinz               Technology and Engineering Director/Consultant
"Starting Startups"                          mailto:Michael.Sinz@sinz.org
My place on the web                      http://www.sinz.org/Michael.Sinz
Received on Mon Mar 5 16:17:35 2007

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