"The objective of this patchset is to keep the system in a state where actions such as page reclaim or memory compaction will reduce external fragmentation in the system," Mel Gorman described his set of thirteen patches labeled "reduce external fragmentation by grouping pages by mobility v30". He explained, "it works by grouping pages of similar mobility together in PAGEBLOCK_NR_PAGES areas." He defined four mobility types as: "UNMOVABLE - Pages that cannot be trivially reclaimed or moved; MOVABLE - Pages that can be moved using the page migration mechanism; RECLAIMABLE - Pages that the kernel can often directly reclaim such as those used for inode caches; RESERVE - The areas where min_free_kbyte-related pages should be stored". Mel added:
"This grouping clearly requires additional work in the page allocator. kernbench shows effectively no performance difference varying between -0.2% and +1% on a variety of test machines. Success rates for huge page allocation are dramatically increased. For example, on a ppc64 machine, the vanilla kernel was only able to allocate 1% of memory as a hugepage and this was due to a single hugepage reserved as min_free_kbytes. With these patches applied, 40% was allocatable as superpages."
Ingo Molnar announced that the real time patchset [story] that he and Thomas Gleixner maintain is now available as a series of 374 broken out patches, "from now on (as of 126.96.36.199-rt2) it will be part of every upstream -rt release and it is available from the -rt download site". Regarding the patches, he notes that it's responsible for, "698 files changed, 27920 insertions(+), 9603 deletions(-)", going on to note, "which is impressive as we moved a huge chunk of -rt into mainline already ;-) The series file is attached below.". Ingo explains:
"the purpose of this finegrained splitup is to foster (even ;-) quicker upstream integration of various -rt features, and to see the full -rt tree integrated upstream. We also hope that this split-up queue helps various vendors standardize their (currently quite splintered) real-time implementations to the upstream -rt patchset. The queue is not (yet) bisectable at every point, and many of the splits are thematic, to allow the simpler future handling of updates."