From 7a39f03bc9da3499c2423758f353ab72d23faa16 Mon Sep 17 00:00:00 2001 From: Pratyush Mallick Date: Fri, 31 Jul 2026 19:37:05 +0000 Subject: [PATCH] mm/page_reporting: add page_reporting_delay_ms module parameter Free page reporting currently hardcodes a 2-second interval between reports. This rigid delay cannot accommodate diverse guest workloads. This patch introduces a module parameter, page_reporting_delay_ms (default: 2000), allowing users to tune the reporting rate: - Lower values enable aggressive memory reclamation by returning unused pages to the host immediately. - Higher values help batch pages during spiky allocation/free churn, reducing hypercalls and nested page fault overheads. Setting the delay to 0 is safe and execution is strictly gated by: - reporting is only triggered by high-order page frees. - expensive hypercalls are bounded by a slot capacity watermark check before proceeding. Link: https://lore.kernel.org/20260731193705.2902728-1-pratmal@google.com Signed-off-by: Pratyush Mallick Reviewed-by: SJ Park Acked-by: Lorenzo Stoakes (ARM) Acked-by: David Hildenbrand (Arm) Cc: Anshuman Khandual Cc: Brendan Jackman Cc: Greg Thelen Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Liam R. Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: SeongJae Park Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Zi Yan Signed-off-by: Andrew Morton --- .../admin-guide/kernel-parameters.txt | 6 ++++ mm/page_reporting.c | 28 ++++++++++++------- 2 files changed, 24 insertions(+), 10 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index b5493a7f8f22..364c2dce8e70 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4810,6 +4810,12 @@ Kernel parameters Adjust the minimal page reporting order. The page reporting is disabled when it exceeds MAX_PAGE_ORDER. + page_reporting.page_reporting_delay_ms= + [KNL] Free page reporting delay in milliseconds + Format: + Adjust the delay in milliseconds between free page + reporting intervals. Default is 2000 (2 seconds). + panic= [KNL] Kernel behaviour on panic: delay timeout > 0: seconds before rebooting timeout = 0: wait forever diff --git a/mm/page_reporting.c b/mm/page_reporting.c index 1cce8729696e..de587be17801 100644 --- a/mm/page_reporting.c +++ b/mm/page_reporting.c @@ -48,7 +48,11 @@ MODULE_PARM_DESC(page_reporting_order, "Set page reporting order"); */ EXPORT_SYMBOL_GPL(page_reporting_order); -#define PAGE_REPORTING_DELAY (2 * HZ) +static unsigned int page_reporting_delay_ms = 2 * MSEC_PER_SEC; +module_param(page_reporting_delay_ms, uint, 0644); +MODULE_PARM_DESC(page_reporting_delay_ms, + "Set page reporting delay in milliseconds"); + static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly; enum { @@ -57,6 +61,13 @@ enum { PAGE_REPORTING_ACTIVE }; +/* schedule work for page reporting */ +static void page_reporting_schedule_work(struct page_reporting_dev_info *prdev) +{ + queue_delayed_work(system_freezable_wq, &prdev->work, + msecs_to_jiffies(page_reporting_delay_ms)); +} + /* request page reporting */ static void __page_reporting_request(struct page_reporting_dev_info *prdev) @@ -77,12 +88,10 @@ __page_reporting_request(struct page_reporting_dev_info *prdev) return; /* - * Delay the start of work to allow a sizable queue to build. For - * now we are limiting this to running no more than once every - * couple of seconds. + * Delay the start of work to allow a sizable queue to build. + * We limit this based on page_reporting_delay_ms. */ - queue_delayed_work(system_freezable_wq, &prdev->work, - PAGE_REPORTING_DELAY); + page_reporting_schedule_work(prdev); } /* notify prdev of free page reporting request */ @@ -337,13 +346,12 @@ static void page_reporting_process(struct work_struct *work) err_out: /* * If the state has reverted back to requested then there may be - * additional pages to be processed. We will defer for 2s to allow - * more pages to accumulate. + * additional pages to be processed. We will defer by + * page_reporting_delay_ms to allow more pages to accumulate. */ state = atomic_cmpxchg(&prdev->state, state, PAGE_REPORTING_IDLE); if (state == PAGE_REPORTING_REQUESTED) - queue_delayed_work(system_freezable_wq, &prdev->work, - PAGE_REPORTING_DELAY); + page_reporting_schedule_work(prdev); } static DEFINE_MUTEX(page_reporting_mutex);