Hello world

Well I integrated a timer interrupt into WoofƆs and got that to work eventually - the MMU makes things like this very fun as I have to map everything I need to use. A few silly bugs in the MMU code didn't help either.

After a 7 hour stint last night I finally booted up an executed a 'user process', including sending it the initial welcome message. It doesn't do much other than call a debug printf function to say hello, but given that it is running in it's own address space successfully that seems a reasonable achievement.

Interrupts are going to be a bit of a pain. Because I want user code to deal with interrupts the kernel has to clear the hardware interrupt status bits itself - which means it needs to know about all the devices that might produce interrupts and how to turn them off. I can't see any way around this right now. I also need some way of letting the user-code know what triggered the interrupt, which is another issue - even with 96 interrupts there is some double-up on the interrupt source. I guess there's always the mailbox idea, or a syscall to query it. There might be some hardware where the interrupt needs processing immediately too, but i'll come to that when I find it.

Hmm, next thing might be to think about devices and get a serial device working.

Timers

Finally got timers `worked out' - i'd played with it before but couldn't get it to work - but it turned out that the code was basically fine, but I had a bug in the irq `enable' routine ... der. They are really rather simple devices that work much the same in almost all microprocessors ever made ..., so it was a bit embarrassing it took this long.

It's using the 32 768Hz clock - which means you have to use some extra hardware logic to get a true 1Khz divisor, but the manual explains that pretty clearly as referenced in the source.

Source is in irq-timer.c.

I'm at the point in WoofƆs that I need at least one timer to get much further so it seemed a good time to poke it into puppybits. I managed to squeeze in a little time to play with WoofƆs over the last few nights and got the code that i'd written a few days ago to load and run - after a stack of mucking about as usual. It doesn't do much - with the trivial round-robin scheduler and no interrupts once the memserver task goes to sleep the idle task starts and is never pre-empted :). I had some linking issues, but the main problem was that for some silly reason I was calling some assembly from C as a function *pointer* not a function and it took me far too long to spot it.

But there's an excuse this time. It's been a really long week - 49 hours of work, quite a few very late nights, an on-site meeting I had to wake up at 7am for, a couple of midnight meetings for GSOC - one of which I missed because I fell asleep, and then I woke up at 2am and didn't crash again till after 8am this morning. Not sure 'tired' covers it. The sunrise wasn't bad though.

Guess which application?

"I have fixed the score on that particular proposal to match the score allotted to it. It is a known issue that occurs randomly sometimes because this particular action is not run in a transaction ."

No comment necessary.

ARGH!

Damnit. Damnit. I need a beer. Oh hang on, I already have one.

Turns out that the algorithm I was converting ... was broken on the C end. No matter how much I tried testing the individual parts, when I turned on the full processing loop it just didn't match. After re-implementing the entire algorithm in both java and c (removing all the layers of abstraction i'd added) they all just checked out - but both produced crap - the original just wasn't doing the same thing at all. Well that was pretty much 2 days wasted, ending in a nasty headache at that.

Well probably more time wasted, as the algorithm I thought actually did something wasn't doing anything useful after-all. Well at least I can re-focus on that, and not waste my time.

Along the way I had a bit of a fight with the swing layout classes. Oddly enough the main memory I have from very first GUI programming I did in uni was how much we all had to fight with the toolkit layout system (well, after just how dreadfully slow it was - something beyond the complexity of gtk but running on a single sparc with 30 other students). Layout always seems to be an issue ... although TBH I think Gtk+ did a reasonable job for the most part - but then again 6 years of programming in it probably helped me forget it's weirdness. I kind of have it working but now when I use a different theme the content renders over the pane border.

Mid-afternoon being stumped I did some work in the yard - clearing some crap out of the way so I can level things off, and started said levelling, so at least my day wasn't a total loss. Although I think I have a bit more earth than I thought I did, so I might have to find somewhere to put it ... I have a rectangle of space I want to put a raised garden bed in, so I might have to look at putting a wall around that now too to hold some of the excess dirt (i'd hoped to leave that for later). I had a dead apricot tree there which i'd almost hacked out (without an axe), and today I managed to break the rest of the roots with some brute force so maybe i've just made myself a heap more work to do! While laying a string-line to get the levels I pinched my finger with a retaining wall block - barely hurt at the time but now I have a huge blood blister on it.

Hmm, the beer's finally starting to work. For a bit there I thought I might need something a bit stronger ...

Melange stinks

So the GSOC project is run on this half-arsed pile of shit called `melange' ('the spice of creation' / 'soc' / geddit?). I've been so utterly and literally dumbfounded by just how poor this application is that I simply haven't been able to find the words to describe it, but I think i'm finally willing to give it a go. But I wont do it on the mailing lists because someone will get offended by the naked truth, and there's already been enough of a shitstorm any time it's mentioned.

... half-arsed

pile of shit

called `melange'

It's very very slow, very ugly, lacks almost all of the basic features you'd expect in any web application developed since about1998, uses javascript where it doesn't need it - interfering with basic browser operation, and is generally an exercise in frustration trying to use it to do basic tasks. And on top of all that the project maintainers seem to be yahoos who like to do things like drop in new versions in a live system in the middle of critical periods of the process, and don't see 6 hours of downtime during said critical limited-time phase as any sort of problem.

Yet when anyone criticises it, the tired old canards of 'send us patches then' 'give us feature requests', and so on get dragged out - at best. Or they get all defensive and agro about it. I believe it's written in Python, so that vastly limits the pool of competent programmers even able to send patches. I believe it runs on googles app server which further limits the programmer pool - both for physical reasons and political ones ('fog computing' et al). And since the application is so poor at demonstrating its basic worth or indeed raison d'être - just why would anyone bother? The latter point is of particular note when it comes to feature requests - if they can't even manage the basics well (after two years?), I have zero confidence they could ever get anything more complex achieved.

This is not some toy project someone is doing in their spare time - this is a production system being used by thousands of people relying on it to ease what is a pretty difficult and tedious process to start with, and to decide how to dole out millions of dollars of real money. It shouldn't be getting in the way at every turn. We shouldn't all be beta testing what is barely a beta-level prototype at this point - this is the second year of it's use, and if that's all I came up with after all that time i'd be seriously consider whether I was capable of ever getting it to work. Even after just one day of failures (like yesterday) i'm questioning my own path.

Some of the mentors were discussing the provision of basic features like history and version control a-la-every-other-document-management-system-since-1970 and Chris Dibona had the inanity to suggest the application needs to `get simpler', not add features! What sort of nonsense is that? The app is difficult to use because it is too simple, remove any one `feature' and it would be utterly worthless - it really does the absolute bare minimum, and does that poorly.

I think what most frustrates me is this attitude more than the application itself - one, that being 'open sauce' you should expect to be a permanent beta-tester of alpha-grade software, and by implication that 'open sauce software' is always barely usable crap (which is clearly quite FUDish). Two, that you're all so privileged that Google is allowing you to bask in their glorious name in any way that you should be thankful for anything they do provide. Third, that is basically works so what are you complaining about. And finally that it's better than what they had before even if it's only because it's not proprietary.

It might not be a Google product, but their name is all over this whole thing and all it does is tarnish that name. As it does of their application server. I just hope I don't have to continue to deal with it beyond the acceptance stage (if I end up being a mentor), but I fear it is a critical component of the entire programme.

ARRGH!

Shit what a day. I've been trying to get some @#$@ algorithm working in Java after converting it from C. I've verified that every stage produces the same numerical result for the same test data, but when run in the application all it produces is total rubbish. I know when I find the problem it'll turn out to be a one line bug somewhere ... i've had more than enough now, i've already spent 5 hours on it, or 7. Time to give it a rest, although I guess it's something to 'look forward to' tomorrow too, because it's a core component and I have to get it working asap. @!#$@

I haven't had much time left over lately to do much beagle hacking but i did a bit more last night - really just getting the last lot of stuff I did to compile, and filling out a few more little details. Although all that late night and tired hacking is certainly going to make for broken code. Next i'll have to get it running on the board - which I imagine will take some time. This includes a user-process as well, so once I get that running I can really start to test everything - mmu code, ipc, and so on. Hmm, still need a jiffy clock though ...

I spent a few hours on the weekend pounding dirt into the dirt - compacting the ground in preparation for levelling it off. Quite surprised at how soft it was - it generally compacted up to 50mm. And this ground was under paving originally ... Also pulled out an old wisteria that i'd soaked up with glycophosphate and thought i'd killed - although it was still well alive under-ground and shooting all along the roots. Bloody hell talk about strong roots (and lots of them), even a pencil sized root was too strong for me to break when it ran too deep to pull further - and I don't think i've put as much effort into anything for quite some time - even the spade had trouble cutting through it.

Cat jumped up on me this morning ... and bloody slipped! In his falling he tried to grab on harder ... damn his claws are sharp. Nice big scratch across my waist ... Still, the Java ended up more painful today.

Java, FFT, Stuff

Just received what appears to be Intel hiring spam on the Beagleboard list. I hope technology like the beagleboard eventually wipes their sorry criminal arses off the planet, the last thing I want is to hear about their stinking jobs.

Blah.

Anyway. Java n stuff.

I kept working on my prototype and added the Apache Maths library mostly because I wanted a simple Complex type that was supposedly written by Java people who know how to write such things. Got a bunch of algorithms converted and just ran it a few times looking at the printf's just to admire my handiwork.

Then I saw the profiler button and thought what the hell, lets see how it works. Well apart from being pretty friggan kick-arse (I can't even remember the last time I ran a profiler over C, but I can tell you it sucked - Visual Studio had absolutely naught without 'paying extra' for some shareware crap) I noticed huge bottlenecks all over the place. For one my image loading was taking about 70% of the time (loads 10 images, does a few fft's over part of them). Well I was flying blind on that one so made a bit of a mess of it. Anyway, did something about that .. next ... the complex arithmetic and the array references were taking all the time. SST arrays are accessed through multi-dimensional capable getters, which are abstracted a couple of levels to an index calculation that loops over an array of strides. Yes very efficient. For some reason I imagined the 'hotspot' compiler could remove all that, but alas it cannot.

Anyway ... to cut a long and rather boring story short, I've thrown away apache.maths's Complex type and written my own that has mutable elements and is used just to hold values. I found a decent FFT library in Java and since that was pretty much the only reason I was using SST I also got rid of that and wrote my own 2D array classes, and re-wrote most of the code to use simple one-dimensional arrays directly.

Man it's ugly code - but it was pretty fugly using apache.maths.complex too - the C is much, much cleaner for the inner loops. For all that it's about 10x faster than it was and on par roughly with the C code (don't quite have the same processing to really compare yet), which i think is worth it. Even if it took most of the day, although I cleaned stuff up as I went too so it wasn't wasted. Well i'm about where I was with the C a week ago, but in the meantime there's been a 4 day long-weekend and now I can easily add GUI. I looked at gtk+ very briefly but it just looked like no fun at all. And besides being cross platform at this point is a big plus.

So along the way I found JTransforms - this is the nice Java FFT library. I'm not sure why it took so long to find - I looked all over the place and all I could find were dinky little implementations. And lots of people looking for decent implementations. And really old stuff. Maybe it's the age of Java, or maybe google just failed me yet again as a search service.Another tool I found along the way was ImageJ - actually I'd looked at it a few weeks ago but not in any great detail. The AWT interface is a bit clunky, but it is pretty fast. From that I worked out how to access the image buffers directly so sped up my image loading about 100x (well I was using 'getpixel' basically, now just a byte array directly). I don't really know if the gimp's implementations are particularly good/bad/or whatever, but doing the same sized guassian filter for example over a 1024x768 image noticeably faster in ImageJ.

... Visual Studio ...

... a rotting pile of

pig shit

Oh here's a funny thing which will probably be very easy to get used to. In the debugger (or even running the code), `fatal' errors like array bounds exceptions don't mean the end of execution. Oh yes I know, welcome to the late 90s, but .NET in VS was a pig, nay a bloaty fat diseased pig, oh lets not mince words; a rotting pile of pig shit, when trying to debug, and fatal errors were fatal too, so I forgot it doesn't have to be that way in so-called 'modern' languages. Not that Netbeans has been too kind to me, I've had a few pointer grabs and it brought system down twice (or maybe SELinux did in its own 'denial of service' attack for added security, if i understood the stack trace at all - it's now disabled), one pointer grab required hitting the power button to reboot, and the other required the reset button as trying to run any programme ended in an oops. Not having much luck debugging threaded code either (it just 'vanishes' if it has a fatal error).

Spent a bunch of time going through some GSOC proposals ... but I don't really know what to say and don't have any examples to go on. Boy that 'melange' thing they're using to track everything is a real crock of shit, really really slow and painful to use - I can't imagine how it works on a project with dozens of proposals. I didn't even realise there were more applications on another page of that fugly 'macos themed' javascript spreadsheet/table view thing it lists everything in.

Oh yeah and so much for getting some dry-work done in the back yard. Later that night it started bucketing down, and bucketing down, and it then rained a lot - around 32mm in a few hours - a lot of rain for here, and particularly loud on a tin roof. Barely a drop for months and then all that. The yard is still totally soaked 2 days later.

That's it for summer I guess.

Daylight savings just finished here - and it's already throwing me out. After plugging away at the computer all afternoon I thought it must've been 10 or something as it seemed to have been dark for so long, but it was only 7:30 ... Good time to call it a day I guess.

Yesterday I got a whole lot of work out of the way on the retaining wall, I should've done more today but I was too lazy. The weather was too nice too - although then I just spent most of the day inside instead of taking advantage of it. Once I sit down to hack it's pretty well game over ... Probably should've made the effort though - looks like weather is turning wet soon, and I need to get some of the stuff done whilst it's still try. Maybe an hour or two over the next two days might do it.

Well that's Easter done, back to work tomorrow.

WoofƆs

Was up pretty late hacking away on some WoofƆs stuff, and then continued it for most of today. For the most part it's just re-arranging stuff I already have from puppybits, or my previous x86 hacking. Pretty time consuming though, trying to tie it all together. It also needed quite a bit of re-thinking and re-jigging along the way.

I've got it all building, and it currently launches two tasks, one which immediately goes to sleep waiting for work to do, and the idle task which blinks the led. But that isn't really any more than I already have in puppybits, so I need to start testing the other stuff - per-process virtual memory, message passing, and so on. These things are a bit hard to play with in isolation since so much support is needed first. Hmm, I really need to get timers and timer interrupts working too, but I can test that in isolation.

The architecture which i've thought about so far does seem to be holding together at least - no big surprises have come along ... yet. Although that assumes the stuff i've written actually works too. So far I have a 'memserver' which is tightly bound to the kernel - it is basically a kernel thread since it accesses the kernel memory directly. It is used to create all in-kernel objects - directly adding them to the kernel in some cases, or where necessary through lightweight system calls to register the new resource. This lets me avoid any dynamic memory in the kernel itself, and by using the right data structures or the occasional lightweight system call I don't have to worry about serialisation either (well, once i've got it right).

I had been thinking about all sort of exotic data structures like trees or hash tables to locate resources based on an object id - but these all have various issues. Execution time, serialisation, and so on (I have implementations that use no dynamic memory, so that wasn't an issue). So in the end I settled for a simple array for many of the objects - it probably uses less memory anyway, and certainly needs less code. It also allows me to update and access it atomically from multiple threads of execution without trouble.

The whole 'kernel' is only 10 system calls so far - and although I still need a few more for interrupts, it shouldn't be many ... I think. Of course most of the work is in the servers, and the kernel is just passing data around. Even in those 10 I already have some 'helper' syscalls too - they aren't strictly necessary but combine a couple of system calls into one, there is probably scope for some more of those.

I had a little chicken and egg problem with message allocating - you need to send a message to the memory server to allocate new messages before they can be sent via the kernel. I think I have worked out a solution - part of the process start-up will be to send a system message to the new process. This message can then be used to ask for more, or just as a general purpose message container. Still, I might need some other more direct mechanism since message ownership passes every time they are forwarded, and it is possible for them to get `lost'.

I might have to look into a mailbox mechanism I guess, although I don't want to have too many options for IPC. After I'd written the basic message allocation system I thought it would be a bit bulky to do too often - well the point is not to in the first place, but it seemed a bit heavy. I looked into a simpler mechanism of message passing using limited registered arguments. But it just didn't seem that useful - because you can only pass primitive non-pointer types. As soon as you want to pass buffers around the mechanism falls down, and you need even more complex support code (like 'far' copies), which then needs to perform extra security checks, and so on. One `freebie' of the message passing mechanism as i've envisioned it so far is it sort of self-checks. Nothing the kernel deals with needs checking in detail because any addresses are from trusted sources or have already been verified, or just integer representations of virtual addresses it never looks at. And servers can perform fairly cheap checking since all data must fit in a fixed bound.

Might sit on all that for a while now.