The Linux kernel has been updated with several serviceability improvements, chiefly around the kdump and SystemTap features. The kdump enhancements should improve the ability to reliably and quickly create crash dumps that can be analysed offline. The new SystemTap features enable IT professionals to debug a running system in real-time without affecting performance or recompiling.
Linux Kernel Gains Serviceability Features
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2006-12-15 9:54 pmdiegocg
Behind on features (for example: systemtap – kprobes, actually – doesn’t still supports userspace tracing in the mainline kernel, it’s under active development), just kernel tracing. If you google you’ll find plenty of opensolaris blogs explaining how inferior is compared with dtrace right now
But they’re based exactly in the same idea – insert a “tracing point” at runtime anywhere on the memory, so when it’s systemtap + kprobes is complete both implementations shouldn’t be *that* different.
Edited 2006-12-15 22:00
2006-12-16 1:29 ammilek
SystemTap due to its implementation flaws is currently much less safer to use than DTrace. It’s just so easy to crash Linux server by simple mistake (or even not mistake) with SystemTap. I guess SystemTap needs at least another few years to catch-up with DTrace.
The last kernel update screwed up the sound on my Ubuntu Eft box (applied it Wed night). Gonna try recompiling ALSA tonight to see if it fixes it. Don’t know if this only affected Ubuntu distros or if others are having the same problems. For those that haven’t installed the upgrade, be sure to backup your original kernel before applying the update to be on the safe side.
2006-12-15 9:59 pmdiegocg
be sure to backup your original kernel before applying the update to be on the safe side.
Of course you should do that always regardless of anything, specially if you’re recompiling yourself the kernel. There’s a good reason why distro ship kernels instead of asking users to do it – normal people shouldn’t recompile things if they want to keep their systems working. Just like you do with gnome and other software. Kernel isn’t different.
2006-12-15 10:21 pmOMRebel
Why in the world did I get modded down for giving out a heads up on this?
2006-12-15 10:55 pmzztaz
Because it’s off-topic.
Explain the connection between SystemTap and your update.
I wonder why the kernel developers didn’t chose to realize DTrace in the kernel. FreeBSD has it, too. And in a licence clean manner:
DTrace is being ported to FreeBSD in such a way that it will be possible to do a source-level build of the FreeBSD operating system without any of the source files covered by the CDDL. This means that it will still be possible for anyone to produce a release of FreeBSD which contains only BSD licensed source files. Of course such a release won’t have a compiler or linker because those are covered by the GPL.
So why not support something already established, even across platforms?
2006-12-16 1:48 pmDubhthach
>>I wonder why the kernel developers didn’t chose to realize DTrace in the kernel. FreeBSD has it, too. And in a licence clean manner: <<
Because the GPLv2 and CDDL can not be mixed in one project to be “GPL compatable” a license has to allow itself be re-licensed as GPLv2 (eg: MIT/BSD license).
The reason why Dtrace can be included in FreeBSD is because CDDL is a per-file license. The FreeBSD guys only have to release modifications to CDDL files under the CDDL. If for example they were to port XFS code from Linux into FreeBSD they would have to relicense all the FreeBSD kernal code under GPLv2. This doesn’t arise with CDDL.
2006-12-16 4:42 pmFord Prefect
Ok, so the Linux guys could take the BSD-licenced files/code from FreeBSD and release them with GPL, but you wouldn’t be allowed to use/link them to other parts which are still CDDL?
I just wonder, if FreeBSD could take this into mainline kernel, this would mean every kernel-space part of DTrace would be in BSD licence, right? And linking non-GPL _userspace_ files to the kernel interface should be allowed, right? So where does it get stuck?
Thanks for your time answering my questions
2006-12-16 7:11 pmctl_alt_del
“I just wonder, if FreeBSD could take this into mainline kernel, this would mean every kernel-space part of DTrace would be in BSD licence, right?”
No, DTrace (and it’s derivative) is *still* CDDL.
“And linking non-GPL _userspace_ files to the kernel interface should be allowed, right?”
I guess that depends on what you mean by “linking” and to whom you speak to….the answer you get will probably fall into the range of: Absolutely not –to– well, that’s a gray area.
“So where does it get stuck?”
I’m not sure I follow? You want to use DTrace (kernel module) in “userspace”? Not sure what the purpose of that would be?
2006-12-16 8:19 pmFord Prefect
Sorry, I think I misinterpreted what I quoted. I thought, the port would be partially (kernel space) in BSD license, but the quote only states that FreeBSD can still be built _without_ this port, therefor with BSD license…
2006-12-16 10:19 pmDubhthach
>>Ok, so the Linux guys could take the BSD-licenced files/code from FreeBSD and release them with GPL, but you wouldn’t be allowed to use/link them to other parts which are still CDDL?
I just wonder, if FreeBSD could take this into mainline kernel, this would mean every kernel-space part of DTrace would be in BSD licence, right? <<
In theory yes, but having not looked at the project, i don’t know how much of the code is under BSD license. Most of it is of course CDDL.
In sense it’s not been included by default in the mainline kernel, it’ll be there as an option at compile time. So if you want a kernel that is completely BSD licensed you don’t compile in DTrace support (or ZFS support for that matter).
But say if you do include code that is CDDL it just have the so-called “Viral effect” ie. only the files under CDDL stay under CDDL. Obvious the FreeBSD devs are pragmatic to at least give their users a choice of enabling DTrace etc. I wouldn’t hold my breath regarding say OpenBSD including it though as they are fairly hardcore on licensing (witness OpenCVS vs. Gnu-CVS)
2006-12-17 10:06 pmhamster
Very nice explanation…
One thing i don’t understand is this:
“But say if you do include code that is CDDL it just have the so-called “Viral effect””
Whereis the viral effect when it doesnt spred to files linked to it?
No punt intended i just don’t follow you there
How does SystemTap compare to DTrace?