In some scenarios Hyper-V needs to manage memory more tightly, so it needs as much information as possible about unused guest pages. To that end Hyper-V now allows free page reporting in chunks smaller than 2 Mbytes. Because of the performance tradeoffs, we want to make the chunk size configurable. Since there's already a free page reporting module parameter, let's use that rather than creating yet another parameter. Configurable order free page reporting is enabled in page_reporting driver in mm tree. However, changes need to be made in drivers like hyper-v's hv_balloon to make it aware of the page order. These patches add support for the same. In the page_reporting driver(patch 1) we export the page_reporting_order module parameter. Besides this, in the page_reporting module a check is added to ensure that whenever the page_reporting_order value is changed, it is within the prescribed limits. The hv_balloon side changes(patch 2) include consuming the exported page_reporting_order. Making changes in reporting these variable order free pages as cold discard hints to hyper-v and dropping and refining checks that restrict the order to a minimum of 9(default). --- Changes in v2 * Add more details in the cover letter about the motivation * Fix the threading between dependent patches Shradha Gupta (2): mm/page_reporting: Add checks for page_reporting_order param hv_balloon: Add support for configurable order free page reporting drivers/hv/hv_balloon.c | 94 ++++++++++++++++++++++++++++++++--------- mm/page_reporting.c | 50 +++++++++++++++++++--- 2 files changed, 118 insertions(+), 26 deletions(-) -- 2.37.2
