20 Jan
2021
20 Jan
'21
2:28 p.m.
On Wed, Jan 20, 2021 at 8:22 AM Jason Gunthorpe jgg@ziepe.ca wrote:
On Tue, Jan 19, 2021 at 08:43:29PM -0500, Pavel Tatashin wrote:
+.. note::
- Techniques that rely on long-term pinnings of memory (especially, RDMA and
- vfio) are fundamentally problematic with ZONE_MOVABLE and, therefore, memory
- hot remove. Pinned pages cannot reside on ZONE_MOVABLE, to guarantee that
- memory can still get hot removed - be aware that pinning can fail even if
- there is plenty of free memory in ZONE_MOVABLE. In addition, using
- ZONE_MOVABLE might make page pinning more expensive, because pages have to be
- migrated off that zone first.
Just to point out, if anyone is using RDMA/etc with hotplug memory, this series is likekly going to be a major regression for those users.
Right: one is because we now prohibit pinning any pages in a movable zone, second reason is because we now check every page during migration that fixes an existing bug.
Jason