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Re: [Gnu-arch-users] Re: give us a hand with arch

From: Tom Lord
Subject: Re: [Gnu-arch-users] Re: give us a hand with arch
Date: Sat, 27 Sep 2003 11:56:38 -0700 (PDT)

    > From: Momchil Velikov <address@hidden>

    >   Without claiming one or another piece of software has deficiencies,
    > let's say existing filesystems are not the most efficient form of
    > storage organization, as far as arch is concerned.

    >   So, what?

Good performance on small files is not exactly an exotic requirement
unique to arch.   I didn't think it was controversial that this is a
serious limitation of the existing ext* systems -- that improvements
in this area were planned.   

    >   Personally, I wouldn't be worried _that_ much about 10-15% space
    > increase (though 57% is ridiculous), but about the time spent doing
    > open(2) on thousands of files.

Right.  That is a serious issue and we recently killed that
requirement for many of the common cases involving _embedded_
tags. (Additional cases to follow.)

A similar optimization is possible for explicit tags -- that's
something other people could probably work on pretty easily just by
looking at how the optimization works for embedded tags.

That'll reduce the common case cost of reading an explicit tag from
open+read+close to just stat.   At the same time, it avoids the
weirdness of making a special case out of patching manifest files.
(There's still a trade-off there: an additional stat per source file
for each explicitly tagged file....)


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