LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20090825.mp3

For Tuesday, August 25th, 2009, I’m Jon Masters with a summary of today’s LKML traffic.

In today’s issue: AlacrityVM, CFS, and Hardware Breakpoints.

AlacrityVM. Gregory Haskins posted some updated networking benchmarks for his “AlacrityVM” hypervisor, which is a fork of KVM. These were taken after a switch in the original code from get_user_pages to an explicit switch_mm and then a copy_[to|from]_user cycle at the suggestion of Michael Tsirkin. Greg says that the latest changes, “moves us ever closer to the goal of native performance under virtualization”.

CFS. Bharata B Rao posted an RFC patchset implementing CFS Hard limits. This aims to modify CFS such that it will give each task a maximum of the CPU time allocated to it, rather than dividing out available time on a fairness basis. Using this patchset, one can more easily implement pay-per-use and avoid a virtual machine instance from consuming more CPU resources than planned, and also for other purposes. The idea for hard limits was previously discussed in an email thread entitled “CPU hard limits” that Bharata had started back on June 4th. This patchset is an early implementation based upon that RFC.

Hardware Breakpoints. K. Prasad posted some updates to his previous hardware breakpoints API. The latest patches introduce per-cpu kernel-space Hardware Breakpoint requests and allow those kernel breakpoints that are defined to be modified through a new API, for use with the perf tools, that will now be able to set and modify existing hardware breakpoints.

In today’s miscellaneous items: some trivial networking fixes from David Miller, some SPARC fixes from David Miller, a new toggle option to be able to disable IMA at runtime for debugging purposes (due to an ongoing memory leak debugging exercise in Fedora) from Kyle McMartin, some syscall tracing fixes from Frederic Weisbecker (a git tree containing similar fixes – or perhaps identical – to those posted on Monday), a proposed update to console_print such that it would have a printk-like interface from Anirban Sinha, a fix from Yinghai Lu to enable x86 to use hard_smp_processor_id to get the apic id in identify_cpu, version 2 of the fixes from Jan Beulich intended to allow binutils prior to 2.17 to properly link the kernel, some ext3 updates from Jan Kara, version 2 of the O_NOSTD patchset originally posted on Monday from Eric Blake, further work on the walltime timer-source option for ftrace from Zhao Lei, some sound fixes from Takashi Iawai, an infinite loop problem report with checkpatch in post-2.6.28 parsing include/linux/inetdevice.h from Eric Dumazet, and the usual round of craziness from Ingo Molnar (fixes for core kernel, performance counters, timers, tracing, and, of course, also x86).

Finally today, Will Brown had posted a problem report surrounding epoll, claiming that it “frequently fails to notify connects at connect bursts”, to which Davide Libenzi followed up adding that multiple quasi-simultaneous events for the same fd are merged, and giving an example for the correct way to handle POLLIN using a loop to catch all the connect events.

Today’s quote of the day goes to Peter Zijlstra, who implies an obvious love for Christoph Lameter’s enthusiasm for the offline scheduler patchset in saying, “Christoph, stop being silly, this offline scheduler thing won’t happen, full stop. It’s not a maintainable solution, it doesn’t integrate with existing kernel infrastructure, and its plain ugly”.

The latest kernel release is 2.6.31-rc7, which was release last week.

Someone called “mailing54″ (who identifies as “Tobias” but doesn’t bother to list an actual name, or valid whois records from which to obtain a name) reports a regression between rc6 and rc7 of the 2.6.31 kernel. The more recent kernel is apparently unable to boot on a Macbook 2,1 using Debian packages built by the Ubuntu kernel team. Meanwhile, Pawel Golaszewski posted an oops occuring on a variety of kernels after a few minutes indicating serious corruption in pick_next_task_fair which seems a bit like a local system (memory?) issue at first glance.

Rafael J. Wysocki posted a list of regressions between 2.6.29 and 2.6.30 and from 2.6.30 up to 2.6.31-rc7-git2. These show that the number of regressions between 2.6.29 and 2.6.30 has more or less leveled off (still largely affecting individial device drivers, not core kernel), and the number of regressions reported from 2.6.30 up until the current development tree currently is doing a lot better than it has been. The unresolved count actually fell in the latest statistics once again, standing at 26. Some of these include some pretty core kernel regressions that still need love.

Stephen Rothwell posted a linux-next tree for August 25th. Since Monday, the voltage, omap, and tip trees lost their build failures and conflicts and the
total subtree count remains steady at 141 trees.

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