LKML Summary Podcast

Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20090628.mp3

For the weekend of June 28th 2009, I’m Jon Masters with a summary of the weekend’s LKML traffic.

In today’s issue: kerneloops.org weekly report, DRBD, Kmemleak, OOM, performance counters, trying harder, and VFAT.

Kernel Oops reports for the week. Arjan van de Ven posted an analysis of last week’s kerneloops.org reports. He cited a mem_cgroup_add_lru_list list corruption as of concern (asking why this is new), a memcmp in the raid code, and the item he previously brought to attention (get_free_pages) concerning warnings on order > 0 allocations in the low level page allocator. Number one on the list this week was an i915_gem_set_tiling issue.

DRBD. Philipp Reisner reposted (for the first time in 2.6.31) concerning his highly available block device for HA clusters. He says “As the first bit of the DRBD patch already got upstream…it is time to get more of DRBD towards mainline”. He wants the LKML masses to consider the lru_cache next.

Kmemleak. Kmemleak, when enabled in the kernel build configuration, aims to detect runtime leakage of kernel memory. But it can be very noisy and it prints very verbose output, which a number of developers have objected to, including Ingo Molnar (who says he has lost crash information due to that). So various suggestions and patches are floating around to both trim the output, and the rate at which it is produced. One suggestion was also to be able to “watch” potentional leaked regions with some kind of registration interface.

OOM. David Howells spent a long time bi-secting kernels until he found the git commit that has been causing a marked increase in OOM situations. It was a patch from MinChan Kim entitled “vmscan: prevent shrinking of active anon lru list in case of no swap space”. There is an (incorrect) assumption that nr_swap_pages cannot be zero on systems with swap, which it can. So debate is now happening over the best way to fix the patch for systems with swap.

Performance counters. Jaswinder Singh Rajput posted a patch adding support to the “perf” utility for “multiple events in one shot”. He adds new options to display HARDWARE and SOFTWARE events using a command such as “perf state -w hw-events -e all-sw-events” wrapped around “ls” to display a number of stats for the running “ls” command.

Trying harder. Linus Torvalds replied to the ongoing get_page_from_freelist discussion concerning order > 0 GFP_NOFAIL allocations, in which David Rientjes had suggested a __GFP_WAIT allocation set the ALLOC_HARDER bit _if_ it repeats, saying that he “tends to like” the kind of “incrementally try harder” approaches to getting memory in such situations. In part because it ensures fairness – a new thread starting off won’t steal the page that an older thread has just had freed and really needs to grab right away.

VFAT. Andrew Trigell posted an updated CONFIG_VFAT_FS_DUALNAMES patch implementing a new config option. It is now possible to selectively configure whether a Linux system using VFAT will create both long and short (8.3) filename entries for long filenames – with this configuration option disabled, Linux will not create the compatibility short filename alternative on long filename entries. Andrew also posted an FAQ and announced that the Linux Foundation have arranged for John Lanza to serve as a patent attorney and answer legal questions that come up relating to this patch (he was copied on the email and is hopefully ready to handle a volume of LKML traffic).

In today’s miscellaneous items: TSC based udelay should have rdtsc_barrier (Venkatesh Pallipadi), a number of Intel Moorestown boot fixes (Jacob Jun Pan), 62 “remove semicolon” patches (Joe Perches), reposted lockdep DFS to BFS conversion patches (Tom Leiming – claims the implementation is simpler), fixes to the S+Core architecture (Arnd Bergmann), a stop_machine patch for very large CPU count machines suffering from severe cacheline contention (Robin Holt), a triple update from Ingo Molnar (x86, timers, and tracing), some EDAC AMD64 fixes (Borislav Petkov), and SPARC fixes (David Miller). Ben Herrenschmidt requested Linus pull some fixes originally intended for rc1 that weren’t ready in time because he got sick for a couple of days.

Finally today. Various people have been mentioning ext3/4 filesystem errors upon resume from suspend (especially on ATA devices). There is suspected to be a bug somewhere but it is proving fairly ellusive to track down.

In today’s announcements: dm-ioband version 1.12.0 (Ryo Tsuruta, disk bandwidth per partition control packages) and version 3.2g of the loop-AES file/swap crypto package.

The latest kernel release is 2.6.31-rc1, which was released by Linus last week.

Andrew Morton posted an mm-of-the-moment for 2009-06-25-15-49 which contains a number of updates against 2.6.31-rc1.

Stephen Rothwell posted a linux-next tree for June 26th. Since Thursday, it includes a fix for fbdev, and various subtrees gained build failures. The total tree count remains steady at 130 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.