LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20090712.mp3

Would you like to record a 30 second summary of your latest development efforts or favorite patch series? I’m at the Linux Symposium in Montreal, so come find me – I’m in the program(me). Look for the guy with too much coffee.

From Montreal, Canada, for the weekend of July 12th 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: RT deadline scheduling, pipe fds, and SLAB replacements.

Deadline scheduling. Henrik Austad posted an RFC concerning a new scheduling policy/class intended to implement deadline driven scheduling, using a modified version of MLLF (Modified Least Laxity First) called Earliest Failure First (EFF), which orders tasks according to when they will miss their deadlines, not when the actual deadline is. The idea seems quite interesting and has triggered a large amount of discussion both on the LKML and also on the linux-rt Real Time mailing list, both on which the discussion was cross-posted. Amongst the concerns was the issue of priority inversion, but the notion of delaying until the last possible moment lead Peter Zjilstra to suggest that the algorithm would “utterly fall apart on overload and would thus be unsuited for soft-rt loads”.

Pipe fd leaks. Over the past few days, there has been some discussion concerning an fd leak for tasks calling pipe() with an invalid address. A fix was proposed by Changli Gao last week, and brought up again by Amerigo Wang, who suggested a trivial problem with the patch prevented Linus from merging it. In reality, though, it turns out that Linus was actually holding off taking this patch since he feels “If you give a bad area to pipe(), there’s no point in closing the file descriptors. It’s a user-space bug. You got your file descriptors, you just don’t know what the hell they are, because your program is [expletive]“.

SLAB. There is some discussion ongoing about last weeks’ “mudflap” GCC support patches – that aim to add support a feature of the GCC that can track down various memory complications. As part of this discussion – which wound up discussing the need for modifications to alternative SLAB-replacement allocators – came a reminder that one of these would be replacement for SLAB, SLQB, is facing some more delays due to “a bunch of problems” that Nick Piggin is currently working on for 2.6.32. For his part, Pekka Enberg stated that SLAB is going to die in the future, but that “we’re [not] going to blindly remove it if it performs better than the alternatives” in certain situations. In this case, those situations included networking benchmarks.

In today’s miscellaneous items: some perfcounter updates (Ingo Molnar – including the module symbol and annotation support), some ptrace updates for the new S+Core architecture (Liqin Chen), some trivial ALSA fixes (Takashi Iwai), a bunch (32) more MMC updates from Nokia (Adrian Hunter), a cond_resched() optimization removing one conditional in this hot path code (Peter Zijlstra – and some other optimization discussions were triggered as a result of this, even comment cleanup), the usual raft of fixes from Ingo Molnar (tracing, core), some nilsfs2 fixes (Ryusuke Konishi), a new version of the PAT patches (Venkatesh Pallipadi), some DRM fixes (Eric Anholt), MCE cleanups (Andi Kleen), version 9 of the soft limits for memory resource controller partches (Balbir Singh), some block/io bits (Jens Axboe), another version of the kernel command line parsing limitation reduction patch series (Daniel Mierswa), a new rb_for_each helper for generic red/black trees in the kernel library, a series of updates from Greg Kroah-Hartman (USB, driver core, staging), some hwmon fixes, some ftrace fixes (Rakib Mullick), and another general Xen Dom0 rant concerning its interaction with swiotlb.

Finally today, Ingo Molnar posted followed up to the posting of the (smells like ACPI) SFI implementation from Len Brown with a treatise on patch commit quality, and in particular, the use of patch title capitalization. It turns out Ingo has some pretty high standards, even for grammar.

The latest kernel release is 2.6.31-rc2, which was released by Linus on the 4th of July (current actual version post-this date is 2.6.31-rc3).

Stephen Rothwell posted a linux-next tree for July 10th. Since Thursday, the tree still fails to build in an allyesconfig build configuration on powerpc, Linus’ tree lost its build failure, and the ttydev tree lost a conflict. The total sub-tree count is steady at 132 trees in the current compose. There is some discussion suggesting an increase in OOM activity (on hackbench runs) for linux-next 0708 and more recent – the cause is being worked on.

That’s a summary of today’s LKML traffic. For further information visit kernel.org. I’m Jon Masters.