Structure and Interpretation of Computer Programmers

An interesting time if you happen to be an aging startup superserver; Ubuntu are to replace init with Upstart from "Edgy Eft". That’s quite cool, the model in which everything needs to always come up and always in the same order put forward by both styles of init is long dead, and the system V style of init is particularly cumbersome (though someone at Apple clearly liked it, as they had both SystemStarter and watchdog in the past).

I’m actually both surprised and pleased to see a Linux distribution making the jump here, I’ve always considered them fairly conservative (apart from in throwing any old free package into the distribution; I mean from a "core stuff"[*] perspective. I know that FreeBSD attempted something with launchd last Summer, but the latter has too much mach_init magic which can’t cleanly be excised.

[*]now Apple are going to start a CoreStuff API and sue me. Fantastic.

One thing from TFA saddened me (though I really ought to have expected it), and that’s this:

To avoid reinventing the wheel, we first looked at how much effort it would be to use of modify the existing replacements to be able to do this. Sun SMF and Apple launchd were immediately ruled out due to licence issues. It was important for us that the solution be uncontroversially free so that other distributions might adopt it; many had already rejected these for GPL incompatibility reasons.

Yes, it’s the standard "GPL first, utility second" argument. I have a fairly strong opinion here: if something works, and I can see that it works, and it works better than any alternative I have access to, I’ll use it. That’s why I’m posting this from OmniWeb on a Mac, despite [i]there being free web browsers around, [ii]my work involving Linux. I prefer to have access to the source, except where that involves a retrograde step in terms of utility. Anyway, I digress; the point here is that launchd is released under (well, depends which version you look at) the Apache licence, and OpenSolaris under the CDDL; both of which are free software licences, but are incompatible with the GPL on technicalities. That’s nice if you really do want to split hairs, but GNU/Linux (if you like) is supposed to be a usable OS so shouldn’t utility come first? Admit it, how many of you have uninstalled kaffe or gcj and are using the Sun jdk? More to the point, how many of you are using Apache (which is also released under the Apache licence)? It’s time to get over it. I propose that if you want to work on a pure GNU system, you should indeed work on a pure GNU system and hie thineself over to the HURD mailing lists. I fully intend to, if a gobbet of spare time makes itself available soon…but more because I think the HURD’s cool ;-).

You can’t use a java.awt.Color in WebObjects, because to use AWT at all on OS X requires connection to the WindowServer.  And unless you’re mad, you probably aren’t running your WOA as root.  This means I can’t do things like, ooh, I don’t know, making a PDF table have a white border instead of a black one.

Strange things can happen when I get bored.  There’s a great little dashboard widget called WikityWidget, which lets you organise notes like a wiki.  Well, I thought, no point in only having my notes on one computer, why not scrape the wikits out of WW and put them online?

You may be interested in some source code.

tyr:/Library/Parallels root# ls -l
total 16
-rw-rw-rw- 1 root wheel 40 Sep 12 15:52 .dhcp.en2
-rw-rw-rw- 1 root wheel 0 Jul 4 17:10 .dhcpd_configuration
-rw-rw-rw- 1 root wheel 0 Jul 4 17:10 .parallels_common_options
-rw-rw-rw- 1 root wheel 100 Jul 4 22:44 .parallels_license_2.2


I can waste a lot of time if an interesting question gets posed. The most recent culprit was Chris Ridd in uk.comp.sys.mac, wondering aloud if threads ever got shuttled between CPUs on a Mac. Here we go…

It certainly looks like the conditions for doing this through the API can never be met on a real Mac running xnu. All you can do is assign a thread or a task to a processor set, but not a single processor. Unless that processor happens to be the only member of a processor set. Thing is, on xnu there is only one processor set, which encompasses all of the processors. So there’s no way to force your threads onto a particular processor in Mac OS X. The lack of multiple processor sets means that you couldn’t have a box with, for instance, both a G5 and a Xeon running a single kernel, which is kindof sad in a way. It won’t get missed, though.

It doesn’t even look like there’s an API to work out which CPU you’re currently on. What you can do is get the port for the default processor set (the only processor set), then by manually furtling with the structs you can iterate through the CPUs (or you can ask your own mach_host_port for an array of the CPU ports). For each CPU you can get the thread queue, which you could compare with your own thread to see if it’s the same. That’d be tedious, but would get the required information. Once there though, I don’t see any way for the thread to move between any queues except the idle and run queues on its ‘native’ processor; so I think the answer is that no thread ever migrates between CPUs. I may be wrong, and am happy to entertain any information to the contrary.

Unsurprisingly with no API to do what I want, little useful code came out of this exercise. I found out how many cpus the system has, but that’s it really.

Update 2006-09-10 16:25 GMT – I hate this not knowing, so I decided to play the Ask Amit card ;-).

I’ve been trying to reply to bbum’s post, firstly my comments were removed as spam, then he approved them by hand, now they’re gone again. So here they are again.

I wrote [in this blog] much about my experiences getting OPENSTEP/Parallels working. Networking’s fine but slow, graphics is good, mouse is a bit jumpy. I was talking at WWDC with people who say that Microsoft VPC no longer supports OPENSTEP/Mach. You definitely can’t boot native on a new Intel Mac, as there’s no SATA driver (and no way to use a boot floppy).

BTW, the floppy images are available over HTTP from Apple: OPENSTEP floppyimages

I spent a lot of today grokking Distributed Objects to write a FAQ entry on it; link above goes to the new entry. Of course, any comments on it or the rest of the FAQ are welcome…

Sorry, but I was finally pushed into turning magic word input on for comments on this blog. Anyone may still comment, but you need to decode a picture in order to do so.

OK, so I said there was a good reason to set up Þæs Ofereode apart from the bandwidth at SDF not being up to the task, and it’s time to come clean. Yesterday I handed in my notice to my current employers, and I’m off to Opera Telecom to become a QA/Test developer. It looks like I’ll be doing funky things with GNUstep so regular readers of iamleeg will not notice a move away from Objective-C and UNIX related ventings.

Of course this has been brewing for a few weeks, but I wanted to make sure my eyes were crossed and my teas dotted before letting anyone else know. Especially on the big scary intarwebs.

For reasons which will be made clear in an upcoming post (probably next week, I’m off to the ‘sunny’ Vaterland soon) I’m in the process of consolidating all of my website activities (except for bloggage) onto Þæs Ofereode. This also lets me do funky things like svn and mysql hosting which I’ll sort out over time. I have an email address there but currently am seeing inexplicable bounceage so I won’t publicise that yet. The comp.lang.objective-c alt.FAQ‘s new home is also there, because the bandwidth at SDF is too small. When Apple publicised ObjC 2 on their Leopard preview page, my SDF site fell of the intarwebs with people looking to see if I’d written about it. Announcements about the ObjC FAQ move will be made on the newsgroup in due course.