Sysfs. Eric W. Biederman posted a series of twenty patches intended to clean up sysfs and make it a "good citizen" of the VFS layer. With the patchset applied, sysfs has lazy synchronization with VFS data structures using a similar technique to that of distributed filesystems. Eric claims to have been running the patch series for months without incident.
Dynamic percpu. Tejun Heo posted a series of patches implementing a conversion of percpu over to dynamic allocation on most architectures. He cautioned that these patches should not be pulled until the maintainers of alpha and s390 give their signoff. It has been tested on x86_64, compiled only elsewhere.
Performance Counters. Peter Zijlstra posted a series of updates to the in-kernel implementation of hardware Performance Counters. Paul Mackerras followed up in a separate email thread with a RFC patch that implemented dynamically allocated per task perf_counter_context structs as a means to allow transfer of said context struct from one task to another when performing a lazy PMU switch.
KVM. Avi Kivity posted a patch series of 46 KVM patches for the 2.6.31 merge. These included a new mode of instruction emulation, forced flushing of all TLBs once a guest's memory mapping changes, and an additional IA64 dependency upon CONFIG_MODULES, amongst many enhancements. It would be remiss not to also note that ongoing discussion was taking place of the upstream push of various Xen patches - including the /proc/mtrr implementation, and a discussion started by Peter Zijlstra on the relative merits of doing mwait emulation in the hypervisor for guests.
Documentation. Jaswinder Singh Rajput, who has in recent times become very involved in much needed small cleanup work, posted a number of documentation updates, including that covering accounting and connector code.
In today's announcements: Greg Kroah-Hartman (aka Greg K-H) announced the release of stable kernels 188.8.131.52 and 184.108.40.206. Both contain important security fixes and users are encouraged to upgrade as soon as possible. Linux Weekly news for May 20th was released at http://www.lwn.net/.
Stephen Rothwell posted a linux-next tree for Mat 20th. Since Tuesday, the edac-amd tree was undropped, the net tree lost a conflict, and a hack for the block tree was replaced with a pending (merge) fix up. The total number of subtrees remains 138 in today's compose.