LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20090903.mp3

For Thursday, September 3rd, 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: CFQ, Matchreply, PCI, RCU tree scalability, and Tracepoints.

CFQ. Corrado Zoccolo posted an RFC patch series modifying the CFQ IO scheduler to adapt its slice slice dependent upon the number of processes that are currently performing IO. Effectively, rather than using fixed time slices, the IO time slice is scaled to a faction of the number of processes performing IO and rescaled whenever that changes. The attached figures appear impressive.

Matchreply. Tejun Heo posted a simple script that he has been using “for a couple of years now” to solve the problem of receiving many duplicated messages from different mailing lists. It indexes Maildirs and hooks into procmail to catch duplicates and redirect them into a separate folder.

PCI. Tejun Heo posted a two part patch series splitting out pci_add_dynid support from store_new_id such that in-kernel code can add PCI Ids dynamically. It will be used by pci-stub to initialize intial IDs via module parameters and allows one to (for example) prevent built-in drivers from attaching to devices with certain IDs handled by loadable modules.

RCU tree scalability. Paul McKenney replied to Nick Piggin’s earlier RCU tree scalability concerns, saying that he believes that Nick is routinely driving up the number of callbacks queued on a given CPU to above 10,000, which would cause excessive calls to force_quiescent_state (400,000 calls per second, for example). He removes the grace period machinery from rcutree __call_rcu, which apparently was a previous effort to avoid implementing synchronize_rcu_expedited.

Tracepoints. Jason Baron, the cunning fox that he can be, posted a 4 part patch series implementing a new “jump label” optimization for tracepoints. The current tracepoint code is implemented using a global variable conditional for each tracepoint, which can become painfully hairy under memory pressure or with large numbers of tracepoints built into the kernel. To better handle this, in discussion with Roland McGrath and Richard Henderson, Jason and co. created a new “asm goto” statement that allows branching to a label. Using some code patching they effectively make switching tracepoints on and off a simple case of patching a jump instruction, conditionally.

In today’s miscellaneous items: some kmemleak patches from Luis R. Rodriguez, some networking updates from David Miller, some sound updates from Takashi Iwai, some AMD Magny-Cours CPU support fixes from Andreas Herrmann, some block fixes for 2.6.31 from Jens Axboe (fixing the max_sectors_kb greater than 512KB issue mentioned previously), another bug report against reading /proc/kcore from Nick Craig-Wood, version 3 of Peter Zijlstra’s load-balancing and cpu_power patches, a fix to allow setrlimit on non-current tasks from Jiri Slaby, a fix to avoid sleeping in TASK_TRACED under the ->cred_guard_mutex lock from Oleg Nesterov, version 3 of the VMware virtual HBA support patches (including relatively minor fixes since version 2) from Alok Kataria, a fix to avoid truncation of the value in abs() if it is greater than 2^32 from Rolf Eike Beer (on 64-bit systems), a bunch of suggestions for asm-generic update candidates in various architecture trees from Robin Getz, and the latest round of rants about Linux software RAID (but on that subject, Dan Williams posted a 29 part patch series beginning the road towards RAID support in ioatdma).

Finally today, Amerigo Wang posted a series of patches inplementing gcov support within kbuild such that “make foo/fbar.c.gcov” becomes possible.

In today’s announcements: Autofs version 5.0.5. Ian Kent announced version 5.0.5 of the autofs utilities. It’s been a long time, apparently, but better late than never, and that update seems fairly comprehensive.

The latest kernel release was 2.6.31-rc8.

Frank A. Kingswood reported another “inconsistend lock state” regression against 2.6.31-rc8, complete with a backtrace, in the JBD code.

Andrew Morton released an mm-of-the-moment for 2009-09-03-16-35.

Greg Kroah-Hartman posted an update on the staging tree for the upcoming 2.6.32 merge window. He reminds everyone that staging is not a dumping ground for dead code (citing the Ethernet Power Link driver as an example of an unmaintained driver that will be removed in the .32 cycle and warning that Android and others face a similar fate in the not too distant future if nothing changes soon).

Stephen Rothwell posted a linux-next tree for September 3rd. Since Wednesday, the xfs, and net trees lost their issues, while the acpi, security-testing, tip, percpu and sfi trees gained several problems. The total subtree count remains steady at 141 trees in the latest compose.

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