LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20091104.mp3

For Wednesday, November 4th, 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: Cgroups, FatELF, PerCPU MM counters, and Swap.

Cgroups. Balbir Singh posted to let everyone know that discussion is happening concerning the most appropriate place to mount the cgroup filesystem. Since the Linux Filesystem Hierarchy Standard (FHS) was written prior to the existence of cgroups, it has no specific advice, which leads to three alternatives. These are /dev/cgroup, /cgroup, or some place under /sys. Balbir prefers the first option, but that will require some co-operation with udev. He asks for advice from others as to the best place for this to live. Several people seem to be quite happy with /sys/kernel/cgroup (which is not the only filesystem that gets mounted there).

FatELF. Continuing the discussion on the relative merits of “FAT” image files containing multiple ELF objects, Mikulas Patocka made some interesting comments on Linux package managers, describing them as “evil”. In his opinion, FatELF might provide a means to ship single image files containing all of the files an application needs to execute in one object, similar to how Apple and other operating systems already do today. Mikulas is concerned about the relative difficulty Linux users face in installing software not provided by their distribution using package management software. He makes a good point, although FatELF may not be the solution to that particular problem.

PerCPU MM counters. Christoph Lameter, noting that support for generic per-cpu operations is now in the “percpu” and linux-next trees, posted a patch implementing per-cpu mm counters for tasks rather than single entires in mm_struct. This obviates the need for larger SMP systems to perform atomic updates to mm counters and (intuitively) implies a performance improvement. The only downside is occasionally having to iterate over each of these per-cpu values when the actual count values are being requested.

Swap. Following on from the recent discussion about OOM killer behavior and the various metrics that might be used in the future, Kamezawa Hiroyuki posted a patch that exports per-process (task) swap usage statistics via procfs. This happens through the addition of a new “VmSwap” entry in /proc/pid/status.

The latest kernel release is 2.6.32-rc6.

Stephen Rothwell posted a linux-next tree for November 4th. There had been no tree the previous day due to a national holiday in Australia, where he is based (and one trusts the horse race went well, too). Since Monday, there was a new “msm” tree (which is an ARM platform), the PowerPC KVM fix was still required, and a couple of other conflicts went away. The total sub-tree count increased today to 146 trees with the addition of the “msm” tree.

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