On Fri, Sep 6, 2019 at 8:23 AM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > On Fri, Sep 06, 2019 at 07:53:21AM -0700, Alexander Duyck wrote: > > This series provides an asynchronous means of reporting 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 unused page reporting > > > > The functionality for this is fairly simple. When enabled it will allocate > > statistics to track the number of reported pages in a given free area. > > When the number of free pages exceeds this value plus a high water value, > > currently 32, it will begin performing page reporting which consists of > > pulling pages off of free list and placing them into a scatter list. The > > scatterlist is then given to the page reporting device and it will perform > > the required action to make the pages "reported", in the case of > > virtio-balloon this results in the pages being madvised as MADV_DONTNEED > > and as such they are forced out of the guest. After this they are placed > > back on the free list, and an additional bit is added if they are not > > merged indicating that they are a reported buddy page instead of a > > standard buddy page. The cycle then repeats with additional non-reported > > pages being pulled until the free areas all consist of reported pages. > > > > 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 the limit is on how many pages it wants to allocate to > > process the hints. The upper limit for this is based on the size of the > > queue used to store the scattergather list. > > I queued this so this gets tested on linux-next but the mm core changes > need acks from appropriate people. Thanks. I will see what I can do to get some more mm people reviewing these changes. - Alex
