Friday, 8 December 2017


Well i've had reason to visit jjmpeg again for something and although it's still doing the job, it's a very very long way behind in version support (0.10.x?). I've added a couple of things here and there (recently AVFormatContext.open_input so I could open compressed webcam streams) but i'm not particularly interested in dropping another release.

But ... along the way I started looking into writing a new version that will be up to date with current ffmpeg. It's a pretty slow burner and i'm going to be pretty busy with something (relatively interesting, moderately related) for the next couple of months.

But regardless here are a few what-if's should I continue with the effort.

  • The old generator + garabage collection support required 4 classes per object.

    1. Abstract autogenerated native WeakReference based accessors with native-oriented methods (passing `pointers').
    2. Manually written native accessors as above and the glue to make it all work.
    3. Abstract autogenerated public accessors with public-oriented methods (passing objects).
    4. Manually written public accessors as above and the glue to make it all work.

    Whilst most of it is autogenerated the generator sucks to maintain and it's a bit of a mess. I've also since learnt that cutting down the number of classes is desirable.

    So instead i'll use the "CObject" mechanism with the WeakReference being a simple native pointer holder object which also knows how to free it. In this case at most 2 custom classes are required - one for autogenerated code (if that happens) and any helper/custom code.

    A few things require reflection going this route but the overheads should be acceptable.

  • Native memory was wrapped in native ByteBuffer objects.

    Originally the goal was to have java just access fields directly but in practice this wasn't practical as the structures change depending on the compile options so you end up with both the C and Java code being system specific, and the Java code requires a compiler to implement it (C being handled by gcc). A side-goal was to make the Java library bit-size independent without resoring to long - although that's all ByteBuffer uses.

    Because the objects are just wrapped on the pointer there is the possibility that multiple objects can be created to reference the same underlying C object (e.g. getStreams().get(0) repeated). Whilst this isn't as bad as it sounds one has to ensure the objects aren't holding any of their own state java-side for example. It also turns out that a direct ByteBuffer isn't terribly fast either from the Java side or looking up from the C side (not sure why on the latter).

    CObject just uses a long directly, which also precludes the likelyhood of poking around C internals by accident or otherwise. It also ensures unqiue objects reference unique pointers - this requires some overhead but it isn't onerous.

  • Using two concrete classes per object allowed the internal details of passing pointers (ByteBuffer) around to be hidden from the luser.

    • But it requires a lot of scaffolding! The same method written at least 2 times!
    • Although the C call gets a ByteBuffer directly, looking up the host pointer still requires a JNIEnv callback.

    CObject likewise uses an accessor to retrieve the native pointer, but because it's the super-class of all objects the objects can simply be passed in directly. That is native methods just look like java methods and so there is no need for any trampolines between method interfaces. It does require a bit more support on the JNI side when returning objects, but it's trivial code.

    An alternative would be to use a long and pass that around but then you still need the public/native separation and all the hassle that entails.

  • A lot of the current binding is autogenerated.

    Once the generator was written this was fairly easy to maintain but getting the generator complete enough was a lot of work. The biggest issue is that the api just isn't very consistent, and some just don't map very nicely to a Java api. Things such as out parameters - or worse, absolute snot like like AVDictionary that should never have existed (onya libav!).

    Each case required special-case code in the generator, often extra support code, and sometimes a fall-back to manually writing the whole lot.

    Working with zcl - and in that case the OpenCL apis are much cleaner and consistent - I discovered it was somewhat less work just to do it manually and not really any harder to maintain afterwards. At least in the case of the original ffmpeg the inconistency was simply because it wasn't originally intended as a public library, and I suspect the newer versions might be a bit better.

    I'm still undecided about simple data accessors as a good case can be made for saving the typing if there are many to write. So perhaps they could still be autogenerated (to an abstract super class as now), or they could be parameterised like they are in zcl (i.e. internally getInt(field) with public wrappers). Another half and half option would be to use the C preprocessor to do most of the ugly work and still write the Java headers by hand. Probably the last one.

Does anyone else care?

Friday, 1 December 2017

RAM saga

Powered down last night because of an approaching thunderstorm ... half my ram gone again.

disable_mtrr_cleanup did nothing. disable_mtrr_trim would hang the boot.

I noticed the RAM speed was wrong in the BIOS again so i reset it, and lo and behold it all showed up, but only until the next reboot. Back to bhe BIOS and just changed the ram from one speed to another and back again - RAM returns!


Sunday, 19 November 2017

I hate my life.

And I wish I was dead.

I hate peecees

Well I was up till 3am fucking around with this bloody machine.

After verifying the hardware actually works it seems that the whole problem with my RAM not being found is the damn BIOS. I downloaded a bunch of BIOSs intending to try an older one and realised I hadn't installed the latest anyway. So I dropped than in and low and behold the memory came back. Yay.

So now I had that, I thought i'd try and get OpenCL working again. Ok, installed the latest (17.40) amdgpu-pro ... and fuck. Unsupported something or other in the kernel module. Sigh. I discovered that 17.30 did apparently work ... but it took a bit of digging to find a download link for it as AMD doesn't link to older releases (at this point i also found out midori has utterly shithouse network code. sigh). I finally found the right one (that wasn't corrupt), installed it and finally ...

Oh, back to 3.5G ram again. FAAARK.

At this point the power went out for the whole street so I had a shower using my phone's torch and went to bed.

Did some more digging when I got up (I was going to give up and say fuck it, but i've come this far), tried manually adding the ram using memmap, and finally confirmed the problem was the BIOS. So i tried an older one. That worked.

But only for a while, and then that broke as well. So trying the previous one ... groan.

Mabye it's time to cut my losses, it's already 1pm, the sun is out, heading for a lovely 31 degrees.

I also got rocm installed but i don't know if it works on this hardware, although at least the kernel is running ok so far.

Saturday, 18 November 2017

io scheduler, jfs, ssd

I didn't have much to do today and came across some articles about jfs and io schedulers and thought i'd run a few tests while polishing off a bottle of red (Noons Twleve Bells 2011). Actually i'd been waiting for a so-called "mate" to show up but he decided he was too busy to even let me know until after the day was over. Not like i've been suicidally depressed this week or anything.

The test I chose was to compile open jdk 9 which is a pretty i/o intensive and complex build.

My hardware is a Kaveri A10-7850K APU, "4G" of memory (sigh) on an ITX motherboard, and a Samsung SSD 840 EVO 250GB drive. For each test I blew away the build directory, re-ran configure, set the scheduler "echo foo > /sys/block/sda/queue/scheduler", and flushed the buffer caches "echo 3 > /proc/sys/vm/drop_caches" before running "time make images". I forced all cpu cores to a fixed 3.0Ghz using the performance scheduler.

At first I kept getting ICE's in the default compiler so I installed gcc-4.9 ... and got ICE's again. Inconsistently though, and we all know what ICE's in gcc means (it almost always means broken hardware, i.e. RAM). Sigh. It was afer a suspend-resume so that might've had something to do with it.

Well I rebooted and fudged around in the BIOS intending to play with the RAM clock but noticed I'd set the voltage too low. So what the hell I set it 1.60v and rebooted. And whattyaknow, suddenly I have 8G ram working again (for now), first time in a year. Fucking PCs.

Anyway so I ran the tests with each i/o scheduler on the filesystem and had no ICE's this time (which was dissapointing because it means the hardware isn't likely to be busted afterall, just temperamental). I used the default compiler. As it was a fresh reboot I ran builds from the same 80x24 xterm and the only other luser applications running beyond the panels and window manager were 1 other root exterm and an emacs to record the results.


real    10m39.440s
user    28m55.256s
sys     2m40.140s


real    10m36.500s
user    28m44.236s
sys     2m40.788s


real    10m42.683s
user    28m43.960s
sys     2m41.036s

As expected from the articles i'd read, deadline (not the default in ubuntu!) is the best. But it's hardly a big deal. Some articles also suggested using noop for SSD storage but that is "clearly" worse (oddly that it increases sys time if it doesn't do anything). I only ran one test each in the order shown so it's only an illustrative result but TBH I'm just not that interested especially if the resutls are so close anyway. If there was something more significant I might care.

I guess i'll switch to deadline anyway, why not.

No doubt much of the compilation ran from buffer cache - infact this is over 2x faster than when I compiled it on Slackware64 a few days ago - at the time I only had 4G system ram (less the framebuffer) and a few fat apps running. But I also had different bios settings (slower ram speed) and btrfs rather than jfs.

As an aside I remember in the early days of Evolution (2000-2-x) when it took 45 minutes for a complete build on a desktop tower, and the code wasn't even very big at the time. That dell piece of crap had woefully shitful i/o. Header files really kill C compilation performance though.

Still openjdk is pretty big, and i'm using a pretty woeful CPU here as well. Steamroller, lol. Where on earth are the ryzen apu's amd??

notzed@minized:~/hg/jdk9u$ find . -type f \
  -a \( -name '*.java' -o -name '*.cpp' -o -name '*.c' \) \
   | xargs grep \; | wc -l
(some of the c and c++ is platform specific and not built but it's a good enough measure).

Midori user style

Well I found a way to make Midori usable for me as a browser-of-text using the user stylesheet thing.

Took some theme and stripped out the crap and came up with this ... it turns all the text readable but leaves most of the rest intact which is an improvement on how firefox rendered it's colour and stye overrides. It just overrode everything which broke a lot of style-sheet driven GUI toolkits amongst other sins.

* {
    color: #000 !important;
    text-shadow: 0 0 0px #000 !important;
    box-shadow: none !important;
    background-color: #777 !important;
    border-color: #000 !important;
    border-top-color: #000 !important;
    border-bottom-color: #000 !important;
    border-left-color: #000 !important;
    border-right-color: #000 !important;

div, body {
    background: transparent !important;

a, a * {
    color: #002255 !important;
    text-decoration: none !important;

a:hover, a:hover *, a:visited:hover, a:visited:hover *, span[onclick]:hover, div[onclick]:hover, [role="link"]:hover, [role="link"]:hover *, [role="button"]:hover *, [role="menuitem"]:hover, [role="menuitem"]:hover *, .link:hover, .link:hover * {
    color: #005522 !important;
    text-decoration: none !important;

a:visited, a:visited * {
    color: #550022 !important;

I don't know if i'll stick with it yet but it's a contender, its built-in javascript blocker looks a lot better than some shitty plugin which will break every ``upgrade'' too. It doesn't seem to run javascript terribly fast, but that's the language's fault for being so shithouse.

Friday, 17 November 2017

Silent Spring

Well I finally got tired of Slackware64 - it worked quite well until I upgraded it to 14.2 some weeks ago, and then too much stuff broke - all I could get working was the VESA driver which meant I was back to a single screen, no opencl either. I ended up putting in xubuntu lts (16.4).

The machine is kinda busted anyway one of the DIMM slots doesn't work - the BIOS detects it but Linux throws the memory away for some reason. This happened months ago but I thought i'd give it another go but of course made no progress. Before it vanished it would sometimes show up and then crash if I used too much memory so I think the motherboard slot is shot (either DIMM works ok in slot 0, neither in 1). I'm in no rush to replace it, although 4G is a bit tight at times but it's not like I do much on it other than waste my life browsing shit I don't care about, with the occasional bit of pointless coding thrown in.

I probably wouldn't have bothered with unbuntu (and i really don't like it or other debians as a whole) but I somehow corrupted the BTRFS filesystem (I think modifying it from a live boot ubuntu which necessarily has a different build - it's been solid for years) and completely lost it. Well I was modifying it throwing away junk before I backed it up so I had just backed it up. I think that's my last experiment with BTRFS, i'm back to jfs now.

At least ubuntu installed quickly and easily and all, not too much hassle apart from the boot config. I setup an EFI boot partition which ubuntu automatically placed in /boot/efi but I didn't create a /boot partition where grub expects everything like the jfs module it needs to read the modules directory on the root partition. Sigh. Well after multiple attempts (easily enough booting via the live usb stick) I eventually worked out the grub command lines to install everything in the /boot/efi partition and have it work (I haven't used grub in years and that was pre-grub 2).

Then I had to go through the ritual of removing all the junk and installing useful stuff. Fuckoff pulseaudio, networkmanager, gnome-software (I mean what the fuck is this shit?), the auto updater, install emacs and dev packages, jvm's, netbeans. Then had to go through and fix the colours and fonts in the tools I use, fix the WM theme, etc. Fortunately i've installed 2 other machines not too long ago so it wasn't so painful this time.

And the stupid gtk3 scrollbars - something I noticed earlier but thought was just firefox at fault. Apparently scrollbars are hard to get right. I can only imagine that being the case if you also have trouble putting underpants on in the morning.

Firefox 57 is kinda shit. Infact I'm having to use `Midori' to write this because I can't even login to google from firefox because the login window simply doesn't work. And with the new plugin system it means my most useful plugin - one that toggles the javascript enable flag - is broken. You can get sort of get the same functionality from the new plugins but because of the way it works any site still thinks javascript is still available so might present a different page than if it wasn't; i.e. it just breaks more shit. I dunno, i'll see on that one, i'm reading less and less lately anyway so it might not matter. The whole browser is pretty bloody fugly too, like someone published and early mockup made in a spreadsheet tool.

And apparently firefox dropped alsa support some time ago, I thought the upgrade to Slackware64 14.2 had just broken something else. Actually I kind of like that computers just shut the fuck up (and don't catch you out by going beep) unless they're asked to make noise so it's no big deal. youtube is a bit crap, and particularly shit in a browser, and there isn't really any other valid reason for sound out of a browser.

The only reason I stick with firefox is because you can override the default colours and fonts completely (black on white gives me a fucking headache, as doe tiny or shitty typefaces - black on grey, DejaVu @ 9+ pix everywhere please), and disable javascript (it just makes so much of the web so much cleaner and faster). It also used to work well enough on the few sites I regularly use.

Sigh, i've had a troubled week.