Re: [PATCH v4] mm/page_reporting: Add page_reporting_delay_ms module parameter

["David Hildenbrand (Arm)" <david@kernel.org>]

On 7/31/26 23:34, Andrew Morton wrote:
> On Fri, 31 Jul 2026 19:37:05 +0000 pratmal@google.com wrote:
> 
>> 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.
> 
> This conflcits with the just-upstreamed 0b45f6927a1
> ("mm/page_reporting: use system_freezable_wq to fix UAF during
> suspend")
> (https://lore.kernel.org/20260721005603.1710551-1-linkl@google.com).
> 
> Please review my resolution:
> 
> --- a/mm/page_reporting.c~mm-page_reporting-add-page_reporting_delay_ms-module-parameter
> +++ a/mm/page_reporting.c
> @@ -48,7 +48,11 @@ MODULE_PARM_DESC(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));

^ just double checking whether that is indented properly .


Acked-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David