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Re: Boot poster challenge



On Sun, Nov 21, 2004 at 05:51:49PM +0100, Arjan van de Ven wrote:
> On Sun, 2004-11-21 at 11:28 -0500, Daniel Veillard wrote:
> > while in
> > single user mode and without concurrent activity:
> > 
> > for foo in $list:
> >   cp $foo $foo.new
[...]
> > We could expect filesystems to allocate the new blocks (data and possibly
> > metadata) more or less sequentially on disk. What would led the filesystem
> > code to not be sequential (most of the time assuming a single block device
> > underneath) 
> 
> nope this doesn't work; while each file individually will be sequential,
> they are not sequential on disk. Note: teh files already aren't
> fragmented, at least on my testsystem. 

  yeah, but why does ext3 allocator doesn't allocate consecutive blocks
for such a pattern ? Directory locality ? Still wondering :-) 
It must be possible one way or another to do this without going though
very complex reservation interfaces. The problem is not to 100% garantee
we will not seek at all while going though this bunch of files but
to have only a reasonable amount of seeks. Suppose there is only 10 seeks
instead of a single block that would amount only for 1 tenth of a second
delay on "normal" hardware.

Daniel

-- 
Daniel Veillard      | Red Hat Desktop team http://redhat.com/
veillard redhat com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/


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