Re: Linux-Netbsd huge difference of speed, same hardware

[Pierre Dupond <76nemo76%gmx.ch@localhost>]

Le 04.03.20 à 10:41, Martin Husemann a écrit :
> On Wed, Mar 04, 2020 at 10:07:29AM +0100, Pierre Dupond wrote:
>> Thanks for the tip. It is a little bit faster now
>> but still much less fast than  with Linux.
>
> Just out of curiosity, why are you mising in /dev/urandom here?
> For performance measurements probably /dev/zero is better (but I don't
> know if SD cards optimize all-zero blocks).
>
This is to initialise a cgd partition with random data. One can use the
Netbsd way (by using "dd if=/dev/zero" on a cgd device with a random
key) but since I have initialised firstly the partition (mbr, not BSD)
on Linux I want to compare the same method on both systems.

The difference of speed made me think to an hardware/low level software
problem on Netbsd. I generally prefer BSD flavour to Linux (mainly for
using firewall and some other programs I find a little bit more
convenient). Since this machine will be an important server (but without
too much load), I can tolerate slowness but not hardware problems.
> Is the speed of the card properly detected (i.e. does the dmesg part
> you posted match the marketing numbers from the manufacturer)?
>
>> Why the use of the raw device makes a difference.
>
> It avoids another level of buffering in the kernel.
Thanks, I understand better now why it's interesting to use
the raw device.

Pierre