On 4/24/26 15:49, Kiryl Shutsemau wrote: > On Fri, Apr 24, 2026 at 07:51:44AM -0400, Peter Xu wrote: >> On Fri, Apr 24, 2026 at 11:34:48AM +0100, Kiryl Shutsemau wrote: >>> Both page_idle and the LRUs (legacy or MGLRU) track accesses on physical >>> memory. We need visibility in the virtual address space domain. >> >> Yes they are, but ACCESS bit isn't. > > A-bit is not a reliable signal for userspace working-set tracking > because the kernel itself is a concurrent consumer. Right, I don't think we want to rely on either the A bit just like we don't want to rely on the Dirty bit in other code. (and even SoftDirty bit is a flawed concept)
I do see some value in a reliable RWP mechanism based on uffd. The real question is, how much benefit it would bring (which other use cases could benefit from it). -- Cheers, David
