On Mon, Feb 02, 2026 at 03:45:54PM +0800, Lance Yang wrote: > When freeing or unsharing page tables we send an IPI to synchronize with > concurrent lockless page table walkers (e.g. GUP-fast). Today we broadcast > that IPI to all CPUs, which is costly on large machines and hurts RT > workloads[1]. > > This series makes those IPIs targeted. We track which CPUs are currently > doing a lockless page table walk for a given mm (per-CPU > active_lockless_pt_walk_mm). When we need to sync, we only IPI those CPUs. > GUP-fast and perf_get_page_size() set/clear the tracker around their walk; > tlb_remove_table_sync_mm() uses it and replaces the previous broadcast in > the free/unshare paths.
I'm confused. This only happens when !PT_RECLAIM, because if PT_RECLAIM __tlb_remove_table_one() actually uses RCU. So why are you making things more expensive for no reason?
