LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20091202.mp3

For Wednesday, December 2nd, 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: Alignment, CFS, faults, utrace, and a new kernel release.

Alignment. Tejun Heo and Ingo Molnar had a debate about memory allocations (in the percpu allocator) and the issue of alignment. On UP (non-SMP) systems, the percpu allocator becomes a simple wrapper around kmalloc, but there’s no way to request a larger (than the machine’s minimum natural word) alignment with kmalloc, so users (such as workqueues) that want to rely upon a specific alignment in order to re-use low-order bits of struct pointers for flag purposes may need their own helper, as Tejun suggested in alloc_cwq.

CFS. Nick Piggin posted to let everyone know that he has been looking through some recent scheduler (CFS) patches and notices a number without any good justification for their inclusion, as well as a few that merely tweak tunables, to which he pondered “[a]re people really not reporting enough regressions against CFS that it is time to just tweak things?”.

Faults. Ingo Molnar and Sriphathi Kodi had a dialog about Sripathi’s recent work on futex fault injection. As this week’s Linux Weekly News points out, Ingo essentially rejected this patch because the patch is “butt-ugly” in the sense that it builds upon existing infrastructure Ingo isn’t fond of. There has been some debate over appropriate response when telling someone submitting patches that they have to also go rework and entire subsystem. It isn’t necessarily wrong to do that, but it can be very frustrating for those who don’t have a lot of time to hack on the kernel in the first place.

Utrace. Roland McGrath (who notes that he is traveling at the moment and is therefore going to be a little laggy on replies) provided some context for the merging of utrace and shared some of his frustrations in dealing with many arch maintainers giving conflicting advice, or just being uninterested and not really caring at all. In saying, “we want to do whatever the people want” (Roland and Oleg) are essentially saying they’re done with the open ended debate and perceived lack of action in moving things forward.

Finally today, Maxim Levitsky asked some questions about waiting for kernel events, to which Alan Cox replied with some useful advice, and Maciej W. Rozycki and Ingo Molnar had a debate about the correct possive form of the word “MIPS”, which this author reminds everyone is an acronym.

In today’s announcements: Linux 2.6.32. Linus Torvalds announced the release of the latest (2.6.32) version of the Linux kernel at 9:47pm Best Coast Time (PST). In noting that the release felt “long overdue” due to two empty weeks for Linus (at Kernel Summit and then a Thanksgiving week vacation) he added that the release was in fact less than three months following the 2.6.31 release and so wasn’t actually far from the normal schedule. There were relatively few changes since -rc8, with the notable exception of some last minute fixes to fscache. Linus wasn’t too pleased with the timing of those, and noted again that this is a release without a new filesystem “for once”. Of course, if LogFS gets merged next time, that will changed quite quickly.

GIT 1.6.6.rc1. Junio C Hamano posted the latest version (1.6.6.rc1) of the GIT SCM as used by the Linux kernel community. In the announcement, Junio notes a change to behavior in the “git fsck” command. It will now default to “git fsck –full” and check packfiles, which will mean that it takes longer to complete than it did previously. He also notes that the forthcoming 1.7.0 release will include a number of breaks to backward compatibility (i.e. use in scripts, rather than internal format changes). For example, “git send-email” will now do the right thing and not make deep threads by default, which has annoyed a number of people in the past.

The latest kernel release is 2.6.32.

Stephen Rothwell posted a linux-next tree for December 2nd. Since Wednesday the origin tree lost its build failures, the mips tree lost two conflicts, and the powerpc tree had a build failure for which a commit was revered. The total sub-tee count remains steady at 154 trees. Stephen mentions an interesting blog post (on neuling.org) with some linux-next stats.

That’s a summary of today’s Linux Kernel Mailing List traffic, for further information visit www.kernel.org. I’m Jon Masters.