Re: [PATCH v1 0/4] Allow order zero pages in page reporting

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

On 2/27/26 15:06, Yuvraj Sakshith wrote:
> Today, page reporting sets page_reporting_order in two ways:
> 
> (1) page_reporting.page_reporting_order cmdline parameter
> (2) Driver can pass order while registering itself.
> 
> In both cases, order zero is ignored by free page reporting
> because it is used to set page_reporting_order to a default
> value, like MAX_PAGE_ORDER.
> 
> In some cases we might want page_reporting_order to be zero.
> 
> For instance, when virtio-balloon runs inside a guest with
> tiny memory (say, 16MB), it might not be able to find a order 1 page
> (or in the worst case order MAX_PAGE_ORDER page) after some uptime.
> Page reporting should be able to return order zero pages back for
> optimal memory relinquishment.
> 
> This patch changes the default fallback value from '0' to '-1' in
> all possible clients of free page reporting (hv_balloon and
> virtio-balloon) together with allowing '0' as a valid order in
> page_reporting_register().
> 
> Changes in v1:
> - Introduce PAGE_REPORTING_DEFAULT_ORDER macro (initially set to 0).
> - Make use of new macro in drivers (hv_balloon and virtio-balloon)
> 	working with page reporting.
> - Change PAGE_REPORTING_DEFAULT_ORDER to -1 as zero is a valid
> 	page order that can be requested.
> 
> Yuvraj Sakshith (3):
>   mm/page_reporting: Allow zero page_reporting_order
>   hv_balloon: Change default page reporting order
>   virtio_balloon: Set pr_dev.order to new default

These look like old stats :)

-- 
Cheers,

David