From: Alexander Duyck <alexander.duyck@gmail.com>
To: kvm@vger.kernel.org, mst@redhat.com,
linux-kernel@vger.kernel.org, willy@infradead.org,
mhocko@kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org,
mgorman@techsingularity.net, vbabka@suse.cz
Cc: yang.zhang.wz@gmail.com, nitesh@redhat.com,
konrad.wilk@oracle.com, david@redhat.com, pagupta@redhat.com,
riel@surriel.com, lcapitulino@redhat.com, dave.hansen@intel.com,
wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com,
dan.j.williams@intel.com, alexander.h.duyck@linux.intel.com,
osalvador@suse.de
Subject: [PATCH v14 4/6] mm: Add unused page reporting documentation
Date: Tue, 19 Nov 2019 13:46:40 -0800 [thread overview]
Message-ID: <20191119214640.24996.34494.stgit@localhost.localdomain> (raw)
In-Reply-To: <20191119214454.24996.66289.stgit@localhost.localdomain>
From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
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 <alexander.h.duyck@linux.intel.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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