This series provides an asynchronous means of hinting to a hypervisor that a guest page is no longer in use and can have the data associated with it dropped. To do this I have implemented functionality that allows for what I am referring to as "waste page treatment". I have based many of the terms and functionality off of waste water treatment, the idea for the similarity occured to me after I had reached the point of referring to the hints as "bubbles", as the hints used the same approach as the balloon functionality but would disappear if they were touched, as a result I started to think of the virtio device as an aerator. The general idea with all of this is that the guest should be treating the unused pages so that when they end up heading "downstream" to either another guest, or back at the host they will not need to be written to swap. So for a bit of background for the treatment process, it is based on a sequencing batch reactor (SBR)[1]. The treatment process itself has five stages. The first stage is the fill, with this we take the raw pages and add them to the reactor. The second stage is react, in this stage we hand the pages off to the Virtio Balloon driver to have hints attached to them and for those hints to be sent to the hypervisor. The third stage is settle, in this stage we are waiting for the hypervisor to process the pages, and we should receive an interrupt when it is completed. The fourth stage is to decant, or drain the reactor of pages. Finally we have the idle stage which we will go into if the reference count for the reactor gets down to 0 after a drain, or if a fill operation fails to obtain any pages and the reference count has hit 0. Otherwise we return to the first state and start the cycle over again. This patch set is still far more intrusive then I would really like for what it has to do. Currently I am splitting the nr_free_pages into two values and having to add a pointer and an index to track where we area in the treatment process for a given free_area. I'm also not sure I have covered all possible corner cases where pages can get into the free_area or move from one migratetype to another. Also I am still leaving a number of things hard-coded such as limiting the lowest order processed to PAGEBLOCK_ORDER, and have left it up to the guest to determine what size of reactor it wants to allocate to process the hints. Another consideration I am still debating is if I really want to process the aerator_cycle() function in interrupt context or if I should have it running in a thread somewhere else. [1]: https://en.wikipedia.org/wiki/Sequencing_batch_reactor --- Alexander Duyck (11): mm: Move MAX_ORDER definition closer to pageblock_order mm: Adjust shuffle code to allow for future coalescing mm: Add support for Treated Buddy pages mm: Split nr_free into nr_free_raw and nr_free_treated mm: Propogate Treated bit when splitting mm: Add membrane to free area to use as divider between treated and raw pages mm: Add support for acquiring first free "raw" or "untreated" page in zone mm: Add support for creating memory aeration mm: Count isolated pages as "treated" virtio-balloon: Add support for aerating memory via bubble hinting mm: Add free page notification hook arch/x86/include/asm/page.h | 11 + drivers/virtio/Kconfig | 1 drivers/virtio/virtio_balloon.c | 89 ++++++++++ include/linux/gfp.h | 10 + include/linux/memory_aeration.h | 54 ++++++ include/linux/mmzone.h | 100 +++++++++-- include/linux/page-flags.h | 32 +++ include/linux/pageblock-flags.h | 8 + include/uapi/linux/virtio_balloon.h | 1 mm/Kconfig | 5 + mm/Makefile | 1 mm/aeration.c | 324 +++++++++++++++++++++++++++++++++++ mm/compaction.c | 4 mm/page_alloc.c | 220 ++++++++++++++++++++---- mm/shuffle.c | 24 --- mm/shuffle.h | 35 ++++ mm/vmstat.c | 5 - 17 files changed, 838 insertions(+), 86 deletions(-) create mode 100644 include/linux/memory_aeration.h create mode 100644 mm/aeration.c --
