From: Alexander Duyck <firstname.lastname@example.org> To: email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Cc: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Subject: [PATCH v14 4/6] mm: Add unused page reporting documentation Date: Tue, 19 Nov 2019 13:46:40 -0800 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <email@example.com> From: Alexander Duyck <firstname.lastname@example.org> Add documentation for unused page reporting. Currently the only consumer is virtio-balloon, however it is possible that other drivers might make use of this so it is best to add a bit of documetation explaining at a high level how to use the API. Signed-off-by: Alexander Duyck <email@example.com> --- Documentation/vm/unused_page_reporting.rst | 44 ++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 Documentation/vm/unused_page_reporting.rst diff --git a/Documentation/vm/unused_page_reporting.rst b/Documentation/vm/unused_page_reporting.rst new file mode 100644 index 000000000000..932406f48842 --- /dev/null +++ b/Documentation/vm/unused_page_reporting.rst @@ -0,0 +1,44 @@ +.. _unused_page_reporting: + +===================== +Unused Page Reporting +===================== + +Unused page reporting is an API by which a device can register to receive +lists of pages that are currently unused by the system. This is useful in +the case of virtualization where a guest is then able to use this data to +notify the hypervisor that it is no longer using certain pages in memory. + +For the driver, typically a balloon driver, to use of this functionality +it will allocate and initialize a page_reporting_dev_info structure. The +fields within the structure it will populate are the "report" function +pointer used to process the scatterlist and "capacity" representing the +number of entries that the device can support in a single request. Once +those are populated a call to page_reporting_register will allocate the +scatterlist and register the device with the reporting framework assuming +no other page reporting devices are already registered. + +Once registered the page reporting API will begin reporting batches of +pages to the driver. The API determines that it needs to start reporting by +measuring the number of pages in a given free area versus the number of +reported pages for that free area. If the value meets or exceeds the value +defined by PAGE_REPORTING_HWM then the zone is flagged as requesting +reporting and a worker is scheduled to process zone requesting reporting. + +Pages reported will be stored in the scatterlist pointed to in the +page_reporting_dev_info with the final entry having the end bit set in +entry nent - 1. While pages are being processed by the report function they +will not be accessible to the allocator. Once the report function has been +completed the pages will be returned to the free area from which they were +obtained. + +Prior to removing a driver that is making use of unused page reporting it +is necessary to call page_reporting_unregister to have the +page_reporting_dev_info structure that is currently in use by unused page +reporting removed. Doing this will prevent further reports from being +issued via the interface. If another driver or the same driver is +registered it is possible for it to resume where the previous driver had +left off in terms of reporting unused pages. + +Alexander Duyck, Nov 15, 2019 +
next prev parent reply other threads:[~2019-11-19 21:46 UTC|newest] Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-11-19 21:46 [PATCH v14 0/6] mm / virtio: Provide support for unused page reporting Alexander Duyck 2019-11-19 21:46 ` [PATCH v14 1/6] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck 2019-11-27 13:52 ` Mel Gorman 2019-11-19 21:46 ` [PATCH v14 2/6] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck 2019-11-27 13:54 ` Mel Gorman 2019-11-19 21:46 ` [PATCH v14 3/6] mm: Introduce Reported pages Alexander Duyck 2019-11-27 15:24 ` Mel Gorman 2019-11-27 17:22 ` Alexander Duyck 2019-11-27 18:35 ` Mel Gorman 2019-11-27 21:55 ` Alexander Duyck 2019-11-28 9:22 ` Mel Gorman 2019-11-29 19:25 ` Alexander Duyck 2019-11-19 21:46 ` Alexander Duyck [this message] 2019-11-19 21:46 ` [PATCH v14 5/6] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck 2019-11-19 21:46 ` [PATCH v14 6/6] virtio-balloon: Add support for providing unused page reports to host Alexander Duyck 2019-11-28 15:25 ` David Hildenbrand 2019-11-28 17:00 ` Michael S. Tsirkin 2019-12-04 17:48 ` Alexander Duyck 2019-12-04 17:53 ` Alexander Duyck 2019-11-29 21:13 ` Alexander Duyck 2019-12-01 11:46 ` Michael S. Tsirkin 2019-12-01 18:25 ` Alexander Duyck 2019-12-02 10:43 ` David Hildenbrand 2019-11-19 21:54 ` [PATCH v14 QEMU 1/3] virtio-ballon: Implement support for page poison tracking feature Alexander Duyck 2019-11-19 21:54 ` [PATCH v14 QEMU 2/3] virtio-balloon: Add bit to notify guest of unused page reporting Alexander Duyck 2019-11-19 21:54 ` [PATCH v14 QEMU 3/3] virtio-balloon: Provide a interface for " Alexander Duyck 2019-11-26 12:20 ` [PATCH v14 0/6] mm / virtio: Provide support " David Hildenbrand 2019-11-26 16:45 ` Alexander Duyck 2019-11-27 10:01 ` David Hildenbrand 2019-11-27 17:36 ` Alexander Duyck 2019-11-27 17:37 ` David Hildenbrand
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