Sysadmin: Using cgroups
Valentine Sinitsyn wonders why Oracle doesn’t want publicity for changes it carries out on former Sun technologies, either for bad or for good?
Resources are something limited, but how to enforce these limits? Valentin Sinitsyn explains what you can do to moderate excess Linux process appetites.
Peeking into running production systems is much like changing tyres on a moving car: possible yet rather non-trivial. Back in LXF231, we looked at eBPF, which enables you to carry out a system-wide inspection and profiling session that’s both safe and fast. We also told you that eBPF is conceptually a successor to DTrace, a Solaris technology that debuted in the early 2000s. That issue, we also told you that Oracle is silently shutting down Solaris, and not to expect any more news from that camp. Well, that last bit was apparently a bit wrong…
When Sun Microsystems open-sourced most of Solaris, including ZFS and DTrace, the reason was in part to fight the growing popularity of the open-source Linux rival. So Sun has chosen a free-but-GPLv2-incompatible license: CDDL. There was no single point of view on whether ZFS or DTrace can be a part of the Linux kernel or not, so the reasons for not including them were legal rather than technical. In fact, FreeBSD is shipping both for a long time now.
Now Oracle, which acquired rights to Sun technologies, is silently making another bold move. It’s relicencing the DTrace kernel code, corresponding libraries and tools under GPLv2 and UPL. The actual change happened in August 2017, but it was so quiet that nobody noticed it until February 2018. UPL stands for Universal Permissive License, and it’s also GPLcompliant. Chances are, Oracle is working on integrating
DTrace into the mainline kernel. Previously, DTrace was made available for Linux as a part of the Oracle Unbreakable Linux kernel, thanks to a special CDDL exemption Oracle has granted to itself.
Oracle’s move is, of course, welcome. But, to quote Bernard Shaw: “[Nobel Prize money] is a life-belt thrown to a swimmer who has already reached the shore in safety.” DTrace under GPL is similar. It would have boosted Linux ten years ago, but now it’s more a case of giving away some stuff you don’t need anymore. While Oracle was keeping its crown jewels safe, we’ve acquired our own treasure trove. Now, even a high-level D language like DTrace uses doesn’t feel like a killer feature.