LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20090811.mp3

For Tuesday, August 11th, 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: Kexec, KVM, RTC, and VGA.

Kexec. Amerigo Wang posted two interesting patches for kexec. The first implements the display of a loaded crash kernel’s memory section information in /proc/iomem, while the second allows one to shrink the reserved memory for a crash kernel on an already running system if it is more than enough. For example, if you already had reserved 128MB, but only needed 100MB, you can simply write into sysfs (/sys/kernel/kexec_crash_size) to reclaim 28MB.

KVM. Michael S. Tsirkin posted version 2 of a 2 part patch series implementing a kernel-level virtio server. The main motivation for this effort is to reduce the virtualization overhead for virtio by removing system calls in the data path, without changing the guest system. As he says, for virtio-net, this removes up to 4 system calls *per packet*, which is a very significant performance improvement and should lead to some nice benchmarks. This version has only a few minor improvements from the previous one, such as moving rather than copying fs/aio.c, and removing some debug logging.

RTC. Feng Tang posted an RFC patch series implementing a new generic rtc_ops struct for x86 systems. As Feng points out, most x86 systems get their time keeping information from a Motorola 146818-like RTC device, EFI, or even virtualiation (these come in via get_wallclock/set_wallclock) but in the future there will be other mechanisms also and so Feng implements the ability to register different RTC sources in a generic fashion.

VGA. Dave Airlie posted a patch series that had originally come in from Tiago Vignatti, aimed at implementing VGA arbitration on systems using “legacy” VGA devices. As Dave says, the Resource Access Control (RAC) module inside the X server currently does the task of arbitration when more than one legacy device co-exists on the same machine, but a problem happens when different userspace clients attempt to do the same and so an arbitration mechanism that is independent of the X server is really needed.

In today’s miscellaneous items: an ACPI event notifier for AC/DC connect/disconnect events from Mark Langsdorf, a number of tracing fixes from Frederic Weisbecker that include Jason Baron’s syscall name to number mapping function, some wireless fixes from John Linville, some OCFS2 fixes from Joel Becker, version 2 of the new Winbond IR driver from David Hardeman, a patch allowing architectures (for example, SPARC) to override the default check_for_illegal_area function if it doesn’t work reliably from Joerg Roedel, a fix for userland ABI breakage in gnet_stats_basic that is passed via netlink from Michael Spang, version 4 of the “Help Resource Counters Scale better” patch series from Balbir Singh (which Prarit Bhargava confirmed improved a kernel compile time by around 30 seconds), a patch fixing CPUCLOCK_PROF and CPUCLOCK_VIRT timer precision from Stanislaw Gruszka (who notes that few people use these, but they should probably still be fixed for anyone who does – his posting includes a reproducer), a patch “constifying” various seq_operations structs from James Morris, a patch to print AMD virtualization features such as NPT, LBRV, SVML, and NRIPS in /proc/cpuinfo from Joerg Roedel, some IPC semaphore improvements (aimed to improve the O(n^2) behavior with n waiting processes) from Nick Piggin, a patch disabling cpufreq on 32-bit PowerPC systems from Bastian Blank, a patch adding cache miss and cache references events to performance counters on Pentium-M systems from Ingo Molnar, and a question from Frans Pop (of Ted T’so) as to what happened to the “data=guarded” patches Chris Mason had proposed in April for ext3.

Finally today, Luis R. Rodriguez inquired as to whether there exists a “typedef” removal tool. Presumably this would be a script or program that would look for typedefs and remove or replace them intelligently. If anyone knows of such a tool, do let Luis know about it also.

The latest kernel release is 2.6.31-rc5, which was released over a week ago.

Zdenek Kabelac posted to let everyone know that he is getting a “complete system freeze during reboot – usually just after iptables frees modules”. He posted a kconfig indicating that he is running 2.6.31-rc5. Also, Catalin Marinas posted to let everyone know that LTP on 2.6.31-rc5 on ARM with root NFS generates an oops in __put_nfs_open_context when running diotest4.

Stephen Rothwell posted a linux-next tree for August 11th. Since Monday, the nfdsd, kvm, rr, and staging trees all lost conflicts and/or build failures. The total sub-tree count is steady today at 140 trees.

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