LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20090707.mp3

I’m traveling in Tokyo, Japan this week and still playing catchup with LKML.

For Tuesday, July 7th 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: (very MM heavy), Kmemleak, OOM, SLAB, and Transcendent memory.

Kmemleak. Catalin Marinas and others had a number of discussion concerning kmemleak. Amongst the discussion, it seems that the scanning threads can occasionally trigger RCU stall warnings (there are several patches floating around, including one that does some additional cond_resched() calls). Separately, Catalin posted a possible leak in request_firmware.

OOM. Kosaki Motohiro relied upon the latest “OOM analysis helper patches” to track down another potential cause of increased OOM situations in recent kernels. He discovered that the current reclaim logic doesn’t consider concurrent reclaim and might accidentally OOM on a number of systems.

SLAB. David Rientjes posted several iterations of a patch adding an option to disable high order debugging in the SLAB allocator. This effectively deals with situations such as an allocation of exactly PAGE_SIZE, which might result in the allocation being increased to cope with the debugging metadata when debugging was turned on. With David’s patch applied, the idea is to handle these situations and not add debugging information to the SLAB in this case. I’m pretty convinced that similar discussion in the past resulted in a net-dislike for selective debug, but maybe it will be different now.

Transcendent memory. It really does seem to be a VM heavy day today. Dan Magenheimer posted version 2 of his “transcendent memory” or ‘tmem’ patches. These are designed to allow Linux to make use of memory that is of an unknown and dynamically variable size – for example in virtual machine environments where the host provides some memory it may pull at any moment, but which may be helpful temporarily for use as a cache, or similar construct. The patch comes with a detailed summary, though I haven’t read all of it yet.

In today’s miscellaneous items: Version 10 of theioeventfd (formerly iosignalfd) patches (Gregory Haskins), a removal of an extraneous second access_ok() check on reads to /dev/zero (Nikanth Karthikesan), some ksym_tracer fixes (Li Zefan), a fix to resume from suspend when CONFIC_CC_STACKPROTECTOR is enabled (Peter Chubb), a reported regression (apparently since .30 and not recalled in 2.6.29) in leaking of key presses on switching [correction: "virtual terminals" - oops] virtual consoles (Andi Kleen, no doubt Alan will look at this during his pending cleanups – he did post some patches earlier, but they were mostly trivial cleanups), some more trivial cleanups from Jaswinder Singh Rajput, version 4 of a patch adding support for 1GB pages to KVM (Joerg Roedel), a P6 PMU patch that adds support for these older Pentium III systems to the performance counters work that Peter, Thomas, and Ingo are working on (Vince Weaver), a reworked version of memory usage limit notification for memcg (Vladislav Buzov) – which does look pretty cool, and version 2 of the smells-like-ACPI SFI (Simple Firmware Interface) support (Len Brown).

Finally today: It was going to happen sooner or later. Joao Correia posted a patch series increasing the lockdep limits in an effort to reduce the number of false positive warnings that are being generated.

The latest kernel release is: 2.6.31-rc2, which was released by Linus on the 4th of July.

Stephen Rothwell posted a linux-next tree for July 7th. Since Friday, the sfi tree has been dropped (but there was a dialog about this), the tree still fails to build in an allyesconfig build configuration (Stephen notes that this is due to a final link problem), the block tree gained a build failure for which Stephen applied a patch, and the suspend tree lost its conflict. The total sub-tree count in the compose remains steady today at 131 trees.

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