On Thu, May 30, 2019 at 02:53:34PM -0700, Alexander Duyck wrote: > 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. A lovely analogy. > 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. will review the patchset closely shortly. > 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 > > --
