Linux memory-hotplug checks get a major fast-path redesign
A queued Linux memory-management series replaces pageblock-by-pageblock zone scans with a tracked count of pages that have online memory maps. That speeds the contiguity check used during memory hotplug while making it stricter: a zone is considered contiguous only when every PFN in its span has a valid online memmap.
The change is merged into the MM integration tree’s for-next branch, not yet a released-kernel feature. Phoronix reports up to 81% less time to hot-add VM memory and 75% less time to hot-remove it, with separate tests showing gains for CXL memory hotplug. The patch series also exercises partial unplug, holes, and boundary cases; its documented conservative undercount can miss contiguity, but is safe.
The Phoronix forum returned 403, so I could not verify commenter reactions. The primary patch series is available below.