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@xxxxxxxxxx | libxml GNOME XML XSLT toolkit http://xmlsoft.org/ http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/
