On Tue, Jun 25, 2019 at 12:42 AM David Hildenbrand <david@xxxxxxxxxx> wrote: > > On 20.06.19 00:32, 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 occurred 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. > > > > When the number of "dirty" pages in a given free_area exceeds our high > > water mark, which is currently 32, we will schedule the aeration task to > > start going through and scrubbing the zone. While the scrubbing is taking > > place a boundary will be defined that we use to seperate the "aerated" > > pages from the "dirty" ones. We use the ZONE_AERATION_ACTIVE bit to flag > > when these boundaries are in place. > > I still *detest* the terminology, sorry. Can't you come up with a > simpler terminology that makes more sense in the context of operating > systems and pages we want to hint to the hypervisor? (that is the only > use case you are using it for so far) I'm open to suggestions. The terminology is just what I went with as I had gone from balloon to thinking of this as a bubble since it was a balloon without the deflate logic. From there I got to aeration since it is filling the buddy allocator with those bubbles. > > > > I am 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 batch size it wants to allocate to process the hints. > > > > My primary testing has just been to verify the memory is being freed after > > allocation by running memhog 32g in the guest and watching the total free > > memory via /proc/meminfo on the host. With this I have verified most of > > the memory is freed after each iteration. As far as performance I have > > been mainly focusing on the will-it-scale/page_fault1 test running with > > 16 vcpus. With that I have seen a less than 1% difference between the > > 1% throughout all benchmarks? Guess that is quite good. That is the general idea. What I wanted to avoid was this introducing any significant slowdown, especially in the case where we weren't using it. > > base kernel without these patches, with the patches and virtio-balloon > > disabled, and with the patches and virtio-balloon enabled with hinting. > > > > Changes from the RFC: > > Moved aeration requested flag out of aerator and into zone->flags. > > Moved boundary out of free_area and into local variables for aeration. > > Moved aeration cycle out of interrupt and into workqueue. > > Left nr_free as total pages instead of splitting it between raw and aerated. > > Combined size and physical address values in virtio ring into one 64b value. > > Restructured the patch set to reduce patches from 11 to 6. > > > > I'm planning to look into the details, but will be on PTO for two weeks > starting this Saturday (and still have other things to finish first :/ ). Thanks. No rush. I will be on PTO for the next couple of weeks myself. > > --- > > > > Alexander Duyck (6): > > mm: Adjust shuffle code to allow for future coalescing > > mm: Move set/get_pcppage_migratetype to mmzone.h > > mm: Use zone and order instead of free area in free_list manipulators > > mm: Introduce "aerated" pages > > mm: Add logic for separating "aerated" pages from "raw" pages > > virtio-balloon: Add support for aerating memory via hinting > > > > > > drivers/virtio/Kconfig | 1 > > drivers/virtio/virtio_balloon.c | 110 ++++++++++++++ > > include/linux/memory_aeration.h | 118 +++++++++++++++ > > include/linux/mmzone.h | 113 +++++++++------ > > include/linux/page-flags.h | 8 + > > include/uapi/linux/virtio_balloon.h | 1 > > mm/Kconfig | 5 + > > mm/Makefile | 1 > > mm/aeration.c | 270 +++++++++++++++++++++++++++++++++++ > > mm/page_alloc.c | 203 ++++++++++++++++++-------- > > mm/shuffle.c | 24 --- > > mm/shuffle.h | 35 +++++ > > 12 files changed, 753 insertions(+), 136 deletions(-) > > create mode 100644 include/linux/memory_aeration.h > > create mode 100644 mm/aeration.c > > Compared to > > 17 files changed, 838 insertions(+), 86 deletions(-) > create mode 100644 include/linux/memory_aeration.h > create mode 100644 mm/aeration.c > > this looks like a good improvement :) Thanks. - Alex
