LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20090914.mp3

For Monday, September 14th, 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: CFS, Fanotify, Huge pages for device drivers, and kthreads.

CFS vs. BFS. Nikos Chantziaras announced that Phoronix has published some comparison benchmarks between the current mainline CFS task scheduler, and Con Kolivas’ recently announced “BFS” task scheduler. The benchmarks aim to cover “real-life” applications, such as timed compilations, a game, email benchmarks, and so forth. The results speak well for BFS, but this is not a surprise since the tests were performed on an (Ubuntu) desktop system with a hardware configuration friendly toward the design goals for BFS. Without meaning to imply any bias, it is this author’s opinion that such tests should be expanded to cover much larger systems before drawing generalizable conclusions. Having said that, BFS clearly has desktop uses.

Fanotify. Eric Paris wondered aloud whether he should migrate the fanotify implementation away from a combination of use of socket, bind, and setsockopt calls over to set-in-stone system calls. A total of 9 new system calls would be required, and Eric obviously expresses hisitation toward this approach, but he is seeking a “ruling from on high” as to the best direction here.

Huge pages for device drivers. Alexey Korolev posted version 3 of a three part patch series aimed at implementing support for huge TLB mappings for the sharind of data between device drivers and userspace. This is especially useful when a large amount of data needs to be shared, as is the case with (for example) video capture, frame buffer, and other devices. The patches are layered upon Eric Munson’s earlier ANON_HUGETLB patchset. Alexey also posted an example HugeTLB driver that makes use of the latest patch series.

Kthreads. Pavel Vasilyev sent a complaint that the calls to set_user_nice configuring all kernel threads to run with a -5 nice level by default in kthread.c had been removed by Ingo Molnar. In fact, they had been “removed” by Mike Galbraith in the course of another patch since he felt that most kthreads didn’t use enough CPU that their weighting was really an issue in getting their work done. This was disputed by others, including Chris Friesen. Pavel posted some benchmarks and discussed headed toward deciding default priorities for certain kernel threads in particular, such as ksoftirqd.

In today’s pull requests: three viafb trees from Jon Corbet, version 4 of the S+Core architecture support patches from Liqin Chen (based upon work he has been doing with Arnd Bergmann and based against 2.6.31-rc7), some credential and SELinux fixes (originally posted by Eric Paris) from James Morris, some input updates for 2.6.32 from Dmitry Torokhov, a merge plan for sh support in 2.6.32 from Paul Mundt (who says, “better late than never..”) (including support for various new boards and processors, runtime PM support, and a “shiny” new DWARF unwinder), some GFS2 updates from Steven Whitehouse, some nilfs2 updates from Rysuke Konishi, a simple ring buffer PowerPC build failure
fix from Steven Rostedt, some DLM updates for 2.6.32 from David Teigland, some O_SYNC cleanups from Jan Kara, some tracing fixes from Steven Rostedt, part 1 of a number of AMD64 EDAC updates from Borislav Petkov, some SLAB allocator “fixes and cleanups” from Pekka J Enberg, some UDF fixes from Jan Kara, some KVM updates from 2.6.32-rc1 from Avi Kivity (simply another iteration of the previous patches, also including a reminder that Marcelo Tosatti is joining Avi as co-maintainer for KVM), some PM updates for 2.6.32 from Rafael J. Wysocki, a number of updates to Blackfin architecture support for 2.6.32 from Mike Frysinger, some x86/txt (Intel “Trusted eXecution Technology”) patches from Peter Anvin, and another round of security credential fixes from James Morris (including several fixes to the KEYS support that have been posted recently by James Morris).

In today’s miscellaneous items: some fixes to /dev/mem supporting partial read and write operations from Fengguang Wu, a patch to incorporate the currently set ARCH environment variable in the deb-pkg build target by Wei Chong Tan, some tracing fixes from Li Zefan, a macro fix from Ferenc Wagner correcting problems experienced by macro users of the container_of macro, version 2 of the post merge per-bdi writeback patches from Jens Axboe (the aforementioned per-bdi writeback flusher patches having now made their way into mainline – separately Jens wondered what bdev->bd_inode_backing_dev_info was ever intended to be used for), signal tracing in ftrace from Jiri Olsa, the latest version of the IO bandwidth controller and BIO tracking patches (dm-ioband and blkio-cgroup) from Ryo Tsuruta, a number of kbuild updates from Andi Kleen, version 2 of the __builtin_unreachable patches from David Daney (who seems to be in contact with Roland McGrath over Roland’s alternative implementation that only supported the x86 case), version 5 of the reflink system call from Joel Becker (allowing copy-on-write reference-counted links to files), latency tracing histogram support (targeting the preempt-rt kernel patches) for displaying potential and effective wakeup latencies from Carsten Emde, and some further /proc/kmem patches from Fengguang Wu.

Finally today, Nicolas Pitre noted that he has a new email address. This is due to some “problems at cam.org”. His new address is nico@fluxnic.net.

In today’s announcements: The IO Controller Mini-Summit 2009. Ryo Tsuruta announced that there will be a dialin number for those wishing to participate in the IO Controller Mini-Summit, running concurrently with this year’s kernel summit in Tokyo, Japan, on October 17th. Mike Snitzer was one of many who wondered (but in this case, aloud, on LKML itself) why discussion of the various IO controller proposals had to wait until after the 2.6.32 merge window closed, was taking place off LKML, and was happening at a venue where limited participants will be able to attend to offer their input.

The latest kernel release was 2.6.31.

Andrew Morton posted an mm-of-the-moment for 2009-09-14-01-57.

Ingo Molnar found a SLAB corruption bug being reported by kmalloc that happens after about “1000+ successful random bootups” and so is “not bisectable at all”. He believes that it may be related to ongoing security related SLAB troubles, although it doesn’t appear to be directly SELinux at fault. Stephen von Krawzynski reported an issue with the 2.6.31 IPv4 implementation as compared with 2.6.30.X kernels when configuring a particular vlan setup.

Stephen Rothwell posted a linux-next tree for September 14th. Since Friday, the sparc, nfsd, security, tip, and oprofile trees lost their issues, while the rr tree still has a build failure and the block tree gained another. Stephen repeats his standard warning that developers not post patches intended for 2.6.33 until 2.6.32-rc1 has been released, and also notes that a number of build failures are currently bouncing from one tree to another.

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