LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20091102.mp3

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

In today’s issue: BKL, FatELF, Fast symbol resolution, OOM, and Performance benchmarks.

BKL. There is an ongoing effort to remove the BKL (Big Kernel Lock), which is the last stayover from early Linux support for SMP. Discussion of BKL removal was revived during the recent Real Time pre-emption mini-summit, and Jan Blunk is amongst those who have been looking at this from the filesystem level. He posted a series of patches intended to push BKL use down into individual filesystems from the generic kernel code (for example do_new_mount()) that it lives in today. He requests comments.

FatELF. There was some ongoing (and quite considerable) push back against the notion of supporting FatELF binaries. Chris Adams wondered aloud just what the target audience really was? As he sees it, embedded users don’t want the bloat, Enterprise distributions already have specific support processes in place for different architectures, and community distributions aren’t likely to want to deal with the increased build complexity and space requirements. Meanwhile, Alan Cox congratulated Ryan C. Gordon on re-inventing the concept of a directory – since directories already allow one to have multiple versions of a binary installed on a given system and to pick and choose between them. Sure that’s not as shiny as an Applesque approach, but it has worked for many decades at this point, and most of the distributions implement multi-arch (sometimes called multi-lib) using some kind of similar approach.

Fast symbol resolution. Alan Jenkins posted the latest version of his fast LKM symbol resolution patches. These take advantage of a binary search for symbol resolution at module load time, using a pre-generated (at build time) sorted table of exported kernel symbols. Using this approach, Alan has once again succeeded in reducing overall system boot time slightly on his netbook. The latest version of the patches has seen some limited testing on ARM and has also been built for Blackfin, so it’s not just x86 at this point.

OOM. Kamezawa Hiroyuki posted to let everyone know that he was putting code where his mouth was with a “total renewal” of the OOM killer code. This isn’t complete at this stage, but it is intended to keep the conversation moving. The first patch lays groundwork (including new OOM type classifications), while the second and subsequent patches add the ability to count swap use per process and implement a newly updated badness calculation that uses rss+swap as the base value but also factors in cpusets, and gives tasks a bonus for how far in the past their last allocation occured, and their runtime.

Performance benchmarks. Hitoshi Mitake posted to let everyone know that he has been working on integrating a benchmark subsystem into the existing – and already fairly extensive – “perf” (or performance events) utility. He asked Rusty Russell for permission to pull Rusty’s hackbench code directly into the kernel tree as part of this effort, which can be used by calling “perf bench sched” with whatever parameters one might wish to specify.

Finally today, Tilman Schmidt requests that we draw attention to the Kernel Cleanup wiki that Robert P J Day has been working on. The page at www.crashcourse.ca/wiki/index.php/Kernel_cleanup includes information about unused Kconfig variables, badly referenced ones, and general problems with kernel code that need further investigation in general.

In today’s announcements: LTP. Subrata Modak posted announcing that the Linux Test Project for October 2009 has been released. The latest version includes fixes, 119 test scenarios for EXT4 testing, new GETUID16/GETUID64/GETEUID16 and PTRACE system call tests, and much more. As usual, it is available at http://ltp.sourceforge.net/.

Sysprof. Soeren Sandmann announced version 1.1.4 of the sysprof CPU profiler. This is the latest version to be based upon the rewrite to make use of the new performance counters interface for exposing the low-level hardware counters. Since the previous 1.1.2 release, there have been a number of fixes. A download is available at http://www.daimi.au.dk/~sandmann/sysprof/.

The latest kernel release was 2.6.32-rc5.

Stephen Rothwell posted a linux-next tree for November 2nd. Since Friday, his fixes tree still has that PowerPC KVM fix, while there were a number of arch issues affecting ARM and OMAP in particular. The sub-tree count remains steady today at 145 trees in linux-next.

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