Tuesday, 3 August 2010

Debian Linux on cheap MIPS mini netbook

Computing-wise, I've taken a break from the JamVM/OpenJDK port for a couple of days while I play with my latest toy : a cheap mini-netbook based on a Chinese MIPS clone. It's branded CnMbook, but it's available (or was) under dozens of names.

Yes, it's been available for a while. I first investigated it over a year ago as I wanted a MIPS machine on which I could do the port of the code-copying JIT (I did the MIPS port of JamVM back in 2007, and I've not touched it since). But it was 170 pounds, which was too much for the tiny spec, and I got an EeePC instead.

However, I still don't like Intel, even though it finally became my main architecture in 2008 (albeit AMD). And I like it even less as a mobile processor, as it's the last area where it doesn't dominate.

So what lead to this sudden surge of interest? I've been waiting for years for the fabled ARM-based netbooks, and a couple of weeks ago I saw a cheap WinCE mini-netbook in a local discount shop which I was passing. My brother (the author of SquashFS) thought it shouldn't be too difficult to get Linux working on it. This lead to a weekend long investigation, which showed up some startling results.

The mini-netbooks appear to be based on one of two ARM9-based SoCs (so these still aren't the low-cost Cortex A8 ones I've been waiting for). Either the Anyka AK7802 or Via's WonderMedia VT8505 SoC. The amazing thing? There's no publicly available Linux kernel (with source) for any of them. There is a binary-only Android kernel for the VT8505 but no public source. For the AK7802 there's nothing, and as Anyka have not made any SoC documentation publicly available it's likely that there never will be.

In contrast, Ingenic, the maker of the MIPS clone in the CnMbook have made available the full source to their modified kernel, u-boot bootloader, rootfs and applications. It came with CELinux, and an ancient 2.4.20 kernel. But it didn't take my brother long to get a modern-ish 2.6.24 kernel running on it (he's working on 2.6.31), and with Debian MIPS Linux it makes a nice little portable development system. Compiling is rather slow, but vim runs well on console, which is all you need!

The cost? 65 quid off ebay for an ex-display model as you can't buy them anymore, the ARM9 WinCE machines having completely replaced them.

I'll next post my experience of running JamVM/OpenJDK on it :)

Tuesday, 27 July 2010

... a thousand words (JamVM/OpenJDK update 2)

Firstly apologies to the people who commented on my first progress update (18th May). I'd hoped to do a blog update way before now, but I've had a lot less time to work on JamVM/OpenJDK port than I expected...

Xerces Ranby asked:
Does JamVM still produce those quick and fast startup times when using the OpenJDK class libraries compared to the fast startup times obtainable when using GNU Classpath classes?
[best of 3 runs]
rob@traken:~/JAM/tests$ time /usr/lib/jvm/jamvm-openjdk/jre/bin/java -showversion hello
java version "1.6.0_0"
OpenJDK Runtime Environment (IcedTea6 1.6.1) (6b16-1.6.1-3ubuntu1)
JamVM (build 1.5.5-openjdk, inline-threaded interpreter)

Hello World!

real 0m0.046s
user 0m0.030s
sys 0m0.000s

rob@traken:~/JAM/tests$ time jamvm -showversion hello
java version "1.5.0"
JamVM version 1.5.5-devel
Copyright (C) 2003-2010 Robert Lougher
Build information:
Execution Engine: inline-threaded interpreter
Compiled with: gcc 4.5.0 20100211 (experimental)
Boot Library Path: /usr/local/classpath/lib/classpath
Boot Class Path: /usr/local/jamvm/share/jamvm/classes.zip:/usr/local/classpath/share/classpath/glibj.zip

Hello World!

real 0m0.048s
user 0m0.030s
sys 0m0.020s

gnu_andrew asked:
Will JamVM still support GNU Classpath, as CACAO does?
Yes, most definitely. I still consider GNU Classpath as JamVM's main class-library as it's where my chief loyalty lies. On more practical grounds, even after the OpenJDK port is functionally complete it will still be a long time before it is as tested as JamVM/GNU Classpath. FWIW, many embedded systems seem to be quite happy with GNU Classpath. GNU Classpath is considerably smaller "out of the box" and much easier to build...

As far as development is concerned, I've taken a different approach to Cacao. Cacao implements the class-library differences within the VM-specific code using #ifdefs. While there's nothing wrong with that, I personally think it makes the code harder to read, and it's harder to get an overview of the changes.

Instead, I've tried to abstract the differences into a classlib interface. At times this has taken some thought and quite a lot of code re-arranging. If anything it's made the code cleaner, as a lot of the messier details are hidden (in general, I'm not a fan of information hiding, but removal of some of the VMFoo details makes the intent clearer).

Having said that, the classlib interface is mostly driven by the differences between GNU Classpath and OpenJDK as I find them. I'd like to think the interface is reasonably generic, but it will probably need changing if another class-library came along...

Currently the classlib interface has 40 functions, the gnuclasspath directory has 8 files, totalling 2552 LOC, and openjdk 10 files totalling 3491 LOC.

Christian Thalinger (hello, twisti!), linuxhippy (hello, Clemens!), Michael Starzinger (hello, Michi!), Stefan Ring:

Yeah, it's taken a long time, and lots of prevaricating. It's not been quite as boring and tedious as I expected; some of it I've actually enjoyed :) Debian might even re-instate JamVM (sticking pins in the Debian T-shirt I bought at FOSDEM, while looking for the Fedora 13 CDROM).

A picture is worth...

Tuesday, 18 May 2010

JamVM and OpenJDK - Progess Update

Porting JamVM to use the OpenJDK/IcedTea class-library has been on my TODO list for quite a while. It appears on my FOSDEM slides for 2008 and again in 2009. It doesn't this year, as I didn't do a talk. Maybe that's why I've finally got round to doing it. I told Twisti I'd get "Hello World" running in 3 months. I've missed by just over a week, mainly because I only started 2 months ago.
root@traken:/usr/local/jamvm/bin# java -Xbootclasspath:/usr/lib/jvm/java-6-openjdk/jre/lib/rt.jar -Dsun.boot.library.path=/usr/lib/jvm/java-6-openjdk/jre/lib/amd64 -showversion hello
java version "1.6.0_0"
OpenJDK Runtime Environment (IcedTea6 1.6.1) (6b16-1.6.1-3ubuntu1)
JamVM (build 1.5.5-openjdk, inline-threaded interpreter)

Hello World!

There's still quite a lot to do, including finishing off support for reflection and sun.misc.Unsafe but threading, exception handling, library handling, class-loading and the VM bootstrap sequence should be done.