Re: Horrible ftruncate performance

[Szakacsits Szabolcs <szaka@sienet.hu>]

On Sat, 12 Jul 2003, Dieter Nützel wrote:
> > > >>More than 506 times...
> > > >>=> 506.34 seconds (8:26.34) / 0.01 seconds = 50.634 times ;-)))
> > > >
> > > > I guess you mean 50,634 or 50634 times faster? But I'm afraid you
> > > > didn't test what you should have.
>
> Why? Read again. Time decrease from 8 minutes, 26 seconds down to 0,01
> seconds (sometimes 0,00 seconds).

For the same test, with the efficiency patch, Oleg wrote:

	real    0m19.205s
	user    0m0.000s
	sys     0m7.130s

That's a difference what doesn't happen magically, usually. The reason is
one of these,

	1) Oleg's result is incorrect
	2) Your result is incorrect
	3) You use different patches.

> INSTALL/SOURCE> l
> insgesamt 19286
> drwxrwxr-x    2 root     root          168 Jul 11 23:33 .
> drwxr-xr-x    3 root     root           72 Jul  3 01:39 ..
> -rw-r--r--    1 nuetzel  users     1696205 Jul  3 01:32 atlas3.5.6.tar.bz2
> -rw-r--r--    1 nuetzel  users     2945814 Jul  2 02:53 k3b-0.9pre2.tar.gz
> -rw-r--r--    1 nuetzel  users    15078557 Jul  2 03:04 movix-0.8.0rc2.tar.gz
>
> INSTALL/SOURCE> time dd if=/dev/zero of=sparse bs=1 seek=200G count=1 ; time
> sync
> 1+0 Records ein
> 1+0 Records aus
> 0.010u 0.000s 0:00.00 0.0%      0+0k 0+0io 153pf+0w
> 0.010u 0.020s 0:00.02 150.0%    0+0k 0+0io 122pf+0w
>
> INSTALL/SOURCE> l
> insgesamt 19310
> drwxrwxr-x    2 root     root          240 Jul 12 15:01 .
> drwxr-xr-x    3 root     root           72 Jul  3 01:39 ..
> -rw-r--r--    1 nuetzel  users     1696205 Jul  3 01:32 atlas3.5.6.tar.bz2
> -rw-r--r--    1 nuetzel  users     2945814 Jul  2 02:53 k3b-0.9pre2.tar.gz
> -rw-r--r--    1 nuetzel  users    15078557 Jul  2 03:04 movix-0.8.0rc2.tar.gz
> -rw-r--r--    1 nuetzel  users    214748364801 Jul 12 15:01 sparse

This is ok, however you also claimed 'sparse' used only 8 kB physical disk
space what Oleg refuted it can't be. Conclusion? You used a different
filesystem, not reiser3.

	Szaka