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 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, firstname.lastname@example.org, email@example.com Subject: [PATCH v17 9/9] mm/page_reporting: Add free page reporting documentation Date: Tue, 11 Feb 2020 14:47:30 -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 free 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/free_page_reporting.rst | 41 ++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 Documentation/vm/free_page_reporting.rst diff --git a/Documentation/vm/free_page_reporting.rst b/Documentation/vm/free_page_reporting.rst new file mode 100644 index 000000000000..33f54a450a4a --- /dev/null +++ b/Documentation/vm/free_page_reporting.rst @@ -0,0 +1,41 @@ +.. _free_page_reporting: + +===================== +Free Page Reporting +===================== + +Free 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 +field within the structure it will populate is the "report" function +pointer used to process the scatterlist. It must also guarantee that it can +handle at least PAGE_REPORTING_CAPACITY worth of scatterlist entries per +call to the function. A call to page_reporting_register will register the +page reporting interface 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 will start reporting pages 2 seconds after +the interface is registered and will continue to do so 2 seconds after any +page of a sufficiently high order is freed. + +Pages reported will be stored in the scatterlist passed to the reporting +function 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 free page reporting it +is necessary to call page_reporting_unregister to have the +page_reporting_dev_info structure that is currently in use by free 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 free pages. + +Alexander Duyck, Dec 04, 2019 +
next prev parent reply other threads:[~2020-02-11 22:47 UTC|newest] Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-02-11 22:45 [PATCH v17 0/9] mm / virtio: Provide support for free page reporting Alexander Duyck 2020-02-11 22:46 ` [PATCH v17 1/9] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck 2020-02-11 22:46 ` [PATCH v17 2/9] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck 2020-02-11 22:46 ` [PATCH v17 3/9] mm: Add function __putback_isolated_page Alexander Duyck 2020-02-19 14:33 ` Mel Gorman 2020-02-11 22:46 ` [PATCH v17 4/9] mm: Introduce Reported pages Alexander Duyck 2020-02-19 14:55 ` Mel Gorman 2020-02-20 18:44 ` Alexander Duyck 2020-02-20 22:35 ` Mel Gorman 2020-02-21 19:25 ` Alexander Duyck 2020-02-21 20:19 ` Mel Gorman 2020-02-11 22:46 ` [PATCH v17 5/9] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck 2020-02-11 22:46 ` [PATCH v17 6/9] virtio-balloon: Add support for providing free page reports to host Alexander Duyck 2020-02-11 22:47 ` [PATCH v17 7/9] mm/page_reporting: Rotate reported pages to the tail of the list Alexander Duyck 2020-02-19 14:59 ` Mel Gorman 2020-02-11 22:47 ` [PATCH v17 8/9] mm/page_reporting: Add budget limit on how many pages can be reported per pass Alexander Duyck 2020-02-19 15:02 ` Mel Gorman 2020-02-11 22:47 ` Alexander Duyck [this message] 2020-02-11 22:51 ` [PATCH v17 QEMU 1/3] virtio-ballon: Implement support for page poison tracking feature Alexander Duyck 2020-02-11 22:51 ` [PATCH v17 QEMU 2/3] virtio-balloon: Add support for providing free page reports to host Alexander Duyck 2020-02-11 22:51 ` [PATCH v17 QEMU 3/3] virtio-balloon: Provide a interface for free page reporting Alexander Duyck 2020-02-11 22:53 ` [PATCH v17 QEMU 4/3 RFC] memory: Add support for MADV_FREE as mechanism to lazy discard pages Alexander Duyck 2020-02-11 23:05 ` [PATCH v17 0/9] mm / virtio: Provide support for free page reporting Andrew Morton 2020-02-11 23:55 ` Alexander Duyck 2020-02-12 0:19 ` Andrew Morton 2020-02-12 1:19 ` Alexander Duyck 2020-02-18 16:37 ` Alexander Duyck 2020-02-19 8:49 ` Mel Gorman 2020-02-19 15:06 ` Mel Gorman
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