U-Boot hacking -or- The dbox2 can boot from disk!

Thanks to a kind donator, I now own a Nokia dbox2 with IDE interface. (For those that don't know - the dbox2 is a settop box designed for german paytv 10 years ago in a way that its bootloader would only run signed software. A limitation that was put aside by some cool hackers early in this century. Nowadays it usually runs Linux on its 66MHz powerpc CPU, 32MB RAM and 8MB FLASH ROM. Later some cool guys designed an IDE interface that plugs into the memory expansion slot)

The main use of such an IDE interface for most people is to use the box as a video recorder. However, I am already doing this via the ethernet port, wich is more practical for me than a built in disk.

I would have deemed it much more useful if I was able to boot from the IDE drive, since that would make it much easier to try out new experimental code without needing to upgrade the FLASH image all the time (having the known working version in FLASH as a fallback is mandatory for good WAF).

So I pondered the problem and found out, that people had already implemented basic support for the IDE interface in U-Boot (which is used as a "second stage" bootloader), and it could already access and read the disk.

Unfortunately, U-Boot needs to be in FLASH, and this U-Boot would then only boot from disk.

So I have been hacking on making U-Boot actually read multiple boot command lines (and and option which one to boot as default) from a config file in the /var/ partition of the FLASH which makes it pretty easy to switch the device we boot from. It is now actually similar to the boot process of the Tripledragon.

The only thing that's missing now is a driver for the front panel keys, so that you can change the selection on the fly without using a serial console. That's coming next, after the summer vacation ;)

Back from Linuxtag 2009

I finally managed to upload my slides to the openSUSE Wiki's Linuxtag 2009 page (I actually had nothing to do with openSUSE this year, but somebody had already listed me on that page and it's actually pretty handy to host the slides there). I also uploaded it to the Linuxtag site, but after experiencing really abysmal organisation this year, I doubt that it will appear anywhere there.

The talk was not that exciting in my point of view - "Netbooks" are, in the end, a pretty boring topic to talk about - but the attending crowd seemed to like it, so apparently it was at least entertaining ;)

The event itself was better than what I had expected from the organisation flaws, I did talk to some embedded people and made many interesting contacts, e.g. with beagleboard guys, peple from the openembedded project and of course the cool hackers from coreboot.

So after a disappointing start, Linuxtag 2009 finally ended pretty successfully for me.

Caroline Keating

She describes herself as

I’m just a girl who likes to tinker on her piano at 2 am and make up stories…

And that's what she did (not at 2 am, though) yesterday in Nürnberg's Musikzentrale in a really great concert.

I'll keep it short, it is hard to put into words anyway, but that really was a touching experience. Maybe even more than last year's Leonard Cohen concert in Berlin.

...maybe it is no coincidence that both are from Montreal?

Now only Christian needs to get the Photos posted on his site...which he finally did. Thanks!

BTW: if you wan to see more great concert photo's, Christian Deckelmann's website is a must. (You'd never guess that he is a (really cool btw) network administrator in real life ;-) )

Improving XFS unlink() performance

I knew for quite some time that XFS has an abysmal performance on huge deletes - e.g. deleting a Linux kernel source tree can take several minutes. But when I had to do multiple images with kiwi yesterday on my relatively new server machine at home, it started to really annoy me, so I invested some time to find out if there is a way to improve the situation.
This is what I started from (numbers are from bonnie++):

/dev/sda1 /space3 xfs rw,noatime,nodiratime,noquota 0 0

Version 1.01d       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
server           4G 69024  31 71616  10 32732   6 75462  39 77511   6 120.9   0
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16   341   1 +++++ +++   311   1   340   2 +++++ +++   249   1

The first hint I got from a colleague was to use "logbufs=8" mount option. This increases the number of buffers that XFS uses for its log. Whatever that means. At the first try, it did not change anything until I realized that a "mount -o remount,..." was not enough, I had to unmount and newly mount the filesystem with the option to make it work.
This is the result, still not too impressive with regard to delete performance, the difference might be purely statistical noise:

/dev/sda1 /space3 xfs rw,noatime,nodiratime,logbufs=8,noquota 0 0

bonnie++:
Version 1.01d       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
server           4G 66413  31 68420  10 32467   5 76001  40 77143   6 107.2   0
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16   338   2 +++++ +++   313   1   332   2 +++++ +++   269   1

But the really good results came only after also increasing the logbuffer size with the "logbsize=262144" option:

/dev/sda1 /space3 xfs rw,noatime,nodiratime,logbufs=8,logbsize=256k,noquota 0 0

Version 1.01d       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
server           4G 77932  33 85196  10 32134   6 59205  32 76792   6 184.5   0
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16  1495   5 +++++ +++   848   2  1468   7 +++++ +++   916   3

Now that's a real improvement and I'll keep it like that.

But beware, there are some caveats:

• The file system has to support the larger buffer sizes, which means you need a sufficiently new kernel. As I am running openSUSE 11.1 on this machine, this is not really a problem, but I had to enable the "version 2 log format" with "xfs_admin -j /dev/sda1" because this partition was created using SLES10 and I am not sure if I still would be able to mount it on an old machine.


• It will use more memory. I guess that it needs at least 2 MB (256kB * 8 buffers) per filesystem, probably more. But on a box with 2GB of RAM, I'll gladly spare that for better performance.

One note: those "measurements" were taken on a Core2 Duo machine using an abit IP35-E mainboard. The used disk drive was my old Maxtor STM3500630A 500GB IDE drive. I did not do any statistical corrections etc., so your mileage may vary.

Cross compilers for openSUSE

Based on Torsten Duwe's great work (currently in the Buildservice in home:duwe:crosstools), which is building but not working 100% correctly, I fixed the powerpc version up (I have no other architecture to test on) and put them into the openSUSE Buildservice in home:seife:cross for now.
Get them from here: http://download.opensuse.org/repositories/home://seife://cross/SLE_11
(don't get put off by that SLE_11, the cross compilers should be pretty system agnostic. For testing I ran them on a SLES10 which is probably older than anything you want to use, and they worked just fine)

Edit: I just found out that this only works because I have a patched rpm on my SLES10 which understands lzma compression. I have added SLES10SP2 to the repository so that pre-LZMA-rpm distributions still can use it.

So if you need a powerpc crosscompiler, just add that repository, install packages "cross-powerpc-embed-linux-gnueabi-binutils", "cross-powerpc-embed-linux-gnueabi-gcc", "cross-powerpc-embed-linux-gnueabi-glibc" and "cross-powerpc-embed-linux-gnueabi-kernel-headers" and you are ready to go.
Make sure that /opt/cross/bin is in your $PATH and configure your project for target "powerpc-embed-linux-gnueabi".

Still TODO: get them into a proper semi-official project.

Oh - and of course I already changed my favourite embedded projects so that they are now able to build with an "external" toolchain ;)

Follow-up: using dialup on 11.1 without NetworkManager...

This https://bugzilla.novell.com/show_bug.cgi?id=429772#c22 is the "official" documentation. It's the same what Marius already wrote in his comment on my last post on the topic, but I'll mention it here again, so that it gets found more easily.

How to get the pipe symbol on a US keyboard?

Yesterday at FOSDEM 2009, I was asked in an interview done by linux-community.de's Nils Magnus, "how do you get the pipe symbol on keyboards without that extra key" (which "international" keyboards have, but US keyboards don't).
Apart from that question being off-topic, as the interview was supposed to be about my netbook talk I had held just before, it's funny that I knew the answer offhand, since I am very often in the situation to use a german keymap on a US keyboard. So here it is:

Copy this into your .Xmodmap:

! use altgr-# as pipe - if i have an US keyboard
! without key 86, i can use this as pipe.
keycode 51 = numbersign apostrophe bar bar bar bar

Then make sure that "Xmodmap ~/.Xmodmap" is run during login. I think this is done by /etc/X11/xinit/xinitrc.common, but don't quote me on that.

So now you have the pipe on "AltGr - #" (On a german keyboard. With the US keycaps it is "AltGr - |", which is not too inconvenient).
The "<" and ">" characters, which are also on this key (again, with a german layout), can be easily be typed by "AltGr - Shift - Y" for "<" and "AltGr - Shift - X" for ">".

Maybe this is helpful to somebody besides me.

Have fun ;)