dtrace on Linux

It's still of no practical interest to kernel developers, distributors, enterprise users, and many others. Jon's (not bronson's) comment was totally reasonable in context -- a kernel developers' discussion about what enterprise-funded developers should work on!

But fair enough -- there may be (probably are) others who find linux-dtrace of practical interest.

But arguments 2 and 3 are linked to this -- to the extent that such people use linux-dtrace, the harms described in those arguments swing into effect. To the extent they avoid linux-dtrace, the harms are abated -- with a trade-off: then they lose dtrace's benefits. There's a tragedy of the commons danger here; the costs of supporting inscrutably broken systems and inflammatory bickering are borne by the community, while the benefits of dtrace are received only only by individuals. Plus, people using/supporting linux-dtrace are not doing themselves any favors in the long run, because it's clearly a dead-end; it's better than nothing, but getting a great solution will require abandoning it and switching to one of the other systems that linux-dtrace sucks the oxygen away from.

So I guess 2 & 3 are arguments for why if we encounter someone for whom linux-dtrace is of practical interest, we should attempt to stop them ;-).

>dtrace and ZFS are exactly as legally-portable-to-linux as are proprietary graphics card drivers.

As a side-point, I'm actually not convinced, at least for dtrace. The nvidia driver uses two tricks: it makes a serious attempt not to be a derived work of the kernel, by including a Free shim layer to basically a windows driver. And it's always distributed separately from the kernel -- otherwise you're distributing a combined, thus derived, thus un-distributable, work. Even the little distros that tried to play fast and loose seem to have given in on this point.

Dtrace is far more intrusive than a graphics driver, and in copyright relevant ways -- it needs to muck around with other people's code to put hooks in. That makes both of the above tricks hard to achieve. Maybe not impossible, I don't know. From his rhetoric about licenses, I haven't gotten the impression that Paul Fox is being that careful. I would not tell people that linux-dtrace as it exists is legal to distribute at all without knowing many more details.

>Argument 2 is a strong argument when we're talking about proprietary, closed-source software, but dtrace and ZFS are Free and Open source, so I'm not sure that it would be as fragile and problematic as proprietary drivers.

It's true the problems are worse for proprietary drivers, but they're quite bad even for plain old out-of-tree drivers. (Note part of the discussion above is about RH's systemtap team's trouble keeping sync with mainline!) And worries about license contamination are an extra burden on top of that.

Sorry for nattering on so!
-- Nathaniel